17' Newport 1974 85-HP Evinrude: Performance Data for Stainless Propeller Selection

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Author Topic:   17' Newport 1974 85-HP Evinrude: Performance Data for Stainless Propeller Selection

Jeff posted 05-27-2009 01:40 PM ET (US)
This past weekend I was able to finally get the Newport out on some calm water and get some performance numbers. I finally installed a tachometer over the winter and found it to be time to put it to use.
I ran the boat on calm water with very light wave action. The air temp was in the low 60's and all that was on the boat was myself and about 16 to 18 gallons of fuel. The was no wind and the all the speeds were measured on a GPS. The motor on the boat is a 1974 85-HP Evinrude Starfilte turning an aluminum OMC 13x19 prop, and I run it trimmed a ways up so the bow is high. Here are the numbers:
2500: 16.3mph
3000: 22.2mph
3500: 28.8mph
4000: 34.5mph
4500: 38.4mph
4650: 39.5mph WOT
Though I can not measure the slip it seems as though the prop loses bite after 3,000 to 3,500-RPM, especially when trimmed up like I run. I am looking to invest into a stainless prop and was looking for recommendations on what ones to test.

Cheers,
Jeff Rohlfing

Tohsgib posted 05-28-2009 10:00 AM ET (US)
13.25x17 SST will be fine. Your rpms are too low, check tach setting.
Tom W Clark posted 05-28-2009 10:35 AM ET (US)
Jeff -- You don't measure slip, you calculate it using the propeller calculator:
http://continuouswave.com/cgi-bin/propcalc.pl
4650 RPM at 39.5 MPH (assuming a 2:1 gear ratio) would suggest the slip is less than 6 percent, which does not seem likely, especially with an aluminum prop and your feeling the prop was slipping more as the trim increased.
I agree with Nick, check your tachometer.
Would you verify the gear ratio?
40 MPH is not bad for a 35-year-old 85 HP motor, one that is probably mounted too low for modern propellers.
Jeff posted 05-29-2009 09:04 AM ET (US)
Tom,
How would I confirm what my gear ratio is?
Also, I was told to set the tach on 6 or 12 pulse. Six was way to high so I figured it was 12.
Tom W Clark posted 05-29-2009 10:17 AM ET (US)
The owner's manual for the motor will contain that information.
Who "told" you how the set the tach? What kind if tachometer is it? Did it come with installation instructions?
Tohsgib posted 05-29-2009 11:16 AM ET (US)
Actually Tom...dropping to a 17" would get him close to 5200 which is good for that engine.
Jeff posted 05-29-2009 11:43 AM ET (US)
The tach is a Telefex. Dave at Lockeman's who is my mechanic told me that this specific motor will be a 6 or 12 pulse for the teleflex tach.
I will dig up the manual at home to find out lower unit ratio.
Peter posted 05-29-2009 12:16 PM ET (US)
It was 2:1 out of the factory in 1974.
Jeff posted 05-29-2009 12:20 PM ET (US)
Thanks Peter.
Peter posted 05-29-2009 12:51 PM ET (US)
Your reported performance numbers match up with 2:1 too.
Tom W Clark posted 05-29-2009 01:10 PM ET (US)
I agree the 13-1/4" x 17" SST was the prop to use on the OMC 85/90 HP motors, but if Jeff is only seeing 4650 RPM now with a 19" pitch prop then the drop to a 17" is not going to get him much over 5000 RPM and that motor redlines at 5500 RPM.
Yes, the motor is old but I want to make sure the tach is reading correctly.
Is it possible the existing prop has been worked on with more pitch added?
Tohsgib posted 05-29-2009 01:46 PM ET (US)
Ya never know! I would buy Blackducks alum for $40 and see.
L H G posted 05-29-2009 02:04 PM ET (US)
That engine is performing very close to what many have reported with a new 90 E-tec. So for 5 hp less, and powerhead rated no less, it's doing quite well. Aren't most of the E-tecs running cupped 15" pitch on the 17' hulls?
Tom W Clark posted 05-29-2009 02:43 PM ET (US)
The E-TEC 90 will usually push a Montauk to 42-44 MPH.
15" Stiletto Advantage or 17" OMC/BRP SST/Viper is the usual prop on the 16'-7" models with the E-TEC 90.
Buckda posted 05-29-2009 03:00 PM ET (US)
"Uncertainty...." whispered the serpent. "Surely you can't go that fast with a new E-TEC."
"No indeed. If you powered with a 115 HP 90 HP Optimax, surely you would see the low to mid 50's."
.......
Jeez...it's like playing that old arcade game "Whack-a-mole". You never know when it'll pop up, but you gotta be quick with the stick.....
Jeff posted 05-29-2009 10:11 PM ET (US)
I found the manual and it recommends the wide open throttle rpm range of 4500 - 5500. It also states in the next sentence that the motor should reach 5000 - 5500 for peak power. I believe I have a spare 13.25 x 17 aluminum OMC prop that came with the boat that I will install on the motor and report what I get.
I still can not find any concrete proof on the pulse setting with this motor and tach combination.
Peter posted 05-29-2009 10:41 PM ET (US)
Here, instead of Whack-a-Mole, we play Whack-a-Troll. ;)
The 1974 85 Evinrude had a 92 cubic inch displacement. In 1979 they bumped the displacement of the 85 up to 99 cubic inches and in 1981 the 85 and 100 HP models were consolidated into a 90.
L H G posted 05-30-2009 02:22 AM ET (US)
Way back in 1971, the Lake George (NY) Park Commission cops used Nausets with 135 Evinrudes on them as their patrol boats. Those V-4 suckers would absolutely smoke my Nauset with 6 cylinder Merc 150 Tower on it. Great engine.
brisboats posted 05-30-2009 09:41 AM ET (US)
^^^Thanks for that Larry, I recently sold a member here a very very nice OMC 135 hp and I think he really came by to look at my Mercury inlines.
Jeff, Those are great numbers right out of the gate. Running a manual trim 1976 V-4 85hp on my heavier commercial Montauk I could not do nearly as well.
Brian
Moby Dick posted 05-30-2009 10:21 PM ET (US)
Jeff.......I hit 41 mph with 2 people (400 lbs) on board with my 1979 Johnson 100HP. It is a 13 1/4 x 17 alum and this it at 5,100 rpm. I was told if I went to a stainless to go with a 16. I question if a 85 HP will turn a 13 1/4 X 17 stainless.
Rich
Tohsgib posted 06-01-2009 11:18 AM ET (US)
1971 was still a 125hp OMC, 1973-76 they made the 135's. 1977 it went to a 140 until 1984.
Jeff posted 06-01-2009 09:19 PM ET (US)
Well, I dug around this past weekend and found the other prop. Turns out it is a 13 1/4 x 17 OMC after all. I broke out the file and cleaned up some nicks on the blades and plan to run it this weekend on a local lake. I will take down numbers and report back.
I guess all in all I am happy with the cruising numbers but, expected more at the top end. While I do run at wide open throttle now and then it is not for long periods of time. The thing is our 1984 Montauk with the 1984 Mariner (Merc) 90 Tower would push that hull to 48 - 49 on a standard Quicksilver aluminum prop (I believe it was a 13 x 19). So, that was my bench mark going into this with the Newport. It is all trade off's though. This OMC V4 starts and idles much better with less smoke than the Mariner.
Brian,
Funny Jim commented about the tower you have sitting around when I saw him last weekend. He said he looked at when he bought your 135. I ended up giving him a OEM tilt unit for that motor after he got it.
L H G posted 06-01-2009 11:34 PM ET (US)
Jeff - Comparing an old powerhead rated 92 inch V-4 with a six-cylinder 100 inch Merc 90, propshaft rated, is like apples and oranges! Much greater than the "decal HP" would indicate. To hold that "tower" down to only 90 HP, they had to hold the RPM's down to 5000 max with smaller carb jets and timing changes. With the possible exception of the later 2-stroke Merc 90 3 cylinder, which Clark Roberts here has indicated can also do 48 on a Montauk, there is no other modern 90 that can accomplish that speed on a Montauk as far as I know.
brisboats posted 06-02-2009 01:25 PM ET (US)
Jeff, Thanks that will be a great compliment to Jim's 135hp. Are you running power trim on the Newport?
Brian

Jeff posted 06-02-2009 02:36 PM ET (US)
Brian,
Yes I have the OEM external mount power trim. This is the same unit as what I gave Dunlap. The one I gave him needs the seals replaced on the rams but, I was unable to find anyone to do it. Do you know of anyone?
http://link.brightcove.com/services/player/ bcpid22879159001?bclid=22378947001&bctid=24827451001p
Jeff posted 06-02-2009 02:43 PM ET (US)
Sorry,
I missed up my work links with my other stuff....
Here are is the image
http://smg.photobucket.com/albums/v427/jeff_rohlfing/ 76%20Newport%20Near%20Complete/?action=view¤t=DSC_3639.jpg
brisboats posted 06-02-2009 10:28 PM ET (US)
Jeff, I don't know anyone off hand but will ask Brian at Fairwinds when I see him later this week. Fairwinds is our local Lockeman's. Interested to see if you can dial her in a bit more and hope you do but I think 39mph is darn respectable even if it is a bit shy of the all mighty inline.
Brian
Tom W Clark posted 06-05-2009 10:50 PM ET (US)
Jeff,
Have you run the old OMC 17" aluminum yet?
Jeff posted 06-06-2009 08:31 PM ET (US)
Tom,
I just got back in from running it today. Here are the numbers. Conditions were about the same.
13 1/4" x 17 OMC Aluminum
2000: 7.6mph
2500: 9.2mph
3000: 15.9mph
3500: 22.1mph
4000: 26.7mph
4500: 30.1mph
5000: 33.6mph
5400: 35.3mph WOT
Tohsgib posted 06-07-2009 10:41 AM ET (US)
Again I think with the 17" SST you should see 52-5300 and closer to 38-39mph.
Jeff posted 06-01-2010 02:22 PM ET (US)
This past weekend I was able to run another prop. While I never did record all of the RPM ranges I did see improved results.
The prop was an OMC SST 13 3/8" x 17 which reached a WOT of 5150 RPM and a GPS reading of 40.2mph.
Water conditions had light wave action with air temps in the upper 70's.
I think this is the right prop selection especially after I move the motor up one hole. I am still having a lot of water coming up the cavitation plate.
Tohsgib posted 06-01-2010 02:53 PM ET (US)
That prop will be good.
Tom W Clark posted 06-01-2010 03:01 PM ET (US)
Nice. I does show what a big difference a switch from aluminum to stainless steel can make. I agree, the 17" OMC SST is a good prop and a good fit.
You will not see the full advantage of it until you raise the motor.
Teak Oil posted 06-01-2010 10:05 PM ET (US)
Those are good numbers Jeff, 42mph might be attainable with some more engine height. I can get 46 mph routinely alone with my 90 'Rude, but its 10 years newer and has an adjustable jackplate. With passengers I usually get 43.5-44mph.
brisboats posted 06-02-2010 10:38 AM ET (US)
Looking good Jeff!
My eyes maybe failing but did I read above that LHG admits an OMC 135hp V-4 smoked his Mercury 150hp inline?

Brian
Jeff posted 09-06-2010 10:20 PM ET (US)
Today I was finally able to log a full set of numbers on the 1976 Newport and the 85hp Evinrude Starflite turning the OMC SST 13 3/8" x 17.
Air temps were in the low 70's and so where the water temps. Water conditions were a light chop and slight breeze. Boat had 16 - 17 Gallons of fuel.
2000: 8.5mph
2500: 13.8mph
3000: 20.5mph
3500: 25.6mph
4000: 30.8mph
4500: 34.7mph
5000: 38.4mph
5175: 40.3mph (WOT trimmed all the way out)
At this point I am very happy with this set up...
Tom W Clark posted 09-12-2010 11:16 AM ET (US)
Yes, that is very good performance for a 36 year old 85 HP outboard motor.
It will improve even more once you raise the motor a hole.
64nauset posted 09-15-2010 09:50 AM ET (US)
The tech guy at Stiletto said to expect about a 100rpm gain at WOT for each hole the motor is raised up. I have not tested that theory.
Tom W Clark posted 09-20-2010 08:29 PM ET (US)
On the typical Whaler, only 100 RPM is a rather conservative estimate. Most will see more
Jeff posted 07-01-2011 10:42 PM ET (US)
I raised the motor up one hole this week as it was mounted all the way down. This evening I headed out alone for the first runs with the motor raised.
My test numbers where exactly the same however, the prop was cavitating FAR more during the hole shot, on plane acceleration and in the turns. I would prefer not to move the motor back down. Is there a recommendation on a better prop to cure this cavitation?
dgoodhue posted 07-02-2011 06:02 AM ET (US)
I don't have experience with classsic 16/17 hulls, but I am surprise one hole has cavitation issues. Is the motor trimmed out at all?
A Stiletto 13 1/4" x 15P will have the same RPM range as your 13 3/8" x 17P SST and tolerate one hole higher mounting,
Tom W Clark posted 07-02-2011 11:26 AM ET (US)
There is no way that SST should be losing grip at only one hole up. Even at that motor mounting height a cheap aluminum prop will grip without any trouble.
If you go the 13-1/4" x 15" Stiletto Advantage 4.25 or Turbo 1, you can mount the motor as high as it will go with no loss of grip.
Tohsgib posted 07-04-2011 01:06 AM ET (US)
I agree with Tom that 3/4 of an inch higher should not have any effect on performance like you posted. My engine is close to 5" higher and with a Stiletto prop you would NEVER know.
Jeff posted 08-05-2011 03:01 AM ET (US)
Over Vacation 3 weeks ago I was able to borrow a 13 7/8"x17' Viper with vent holes from Lockeman's hardware and boats. Due to some circumstances I was unable to get full data numbers but, I was able to test the prop. I found that this prop was much larger in mass than my current prop and engaged into gear with a solid thud. Planing was much improved and I was able to planing with out much of any cavitation so long as rolled on the power. If I when to WOT hard it would slip while coming out of the hole.
I was able to hold grip in all turning situations even if I had the motor trimmed out and was on a hard turn in. The current SST blows out in most all turns.
No matter how I had the motor trimmed I was getting 39.5 - 39.9 on the GPS with the Viper. On a side note I was able to see 40.7 this past weekend with my current 13 3/8" x 17" SST once it finally stopped cavititing and held grip.
All in all the Viper was a better option to the current 13 3/8" x 17" SST I have. Though I would still like to try some other props before settling. I hope to try a non-ventilated 13 7/8"x17' Viper as Dave at Lockemans stated that might be the better option and I might not experience the cavitation while planing with that prop. I would also like to try a Stiletto Advantage if I can round on up.
Is there any reason to consider a 4 blade prop?
As for the mounting height. I think I may disagree with the common convention of you can keep going much higher if at all with my motor. In speaking with Dave at Lockemans he said that the old old style lower unit design I have on this 1974 may not tolerate the elevated running height like later designs do.
Tom W Clark posted 08-05-2011 10:40 AM ET (US)
Jeff -- Your motor is only one hole up now and it can go up one or two more holes with the Stiletto Advantage. I have seen this again and again, the OMC/BRP props, while good, will not tolerate as high a motor mounting height.
Some years ago, Rob Schmidt and I tested an SST against a Stiletto Advantage on both a Montauk with an Evinrude and a Sport 15 with an Evinrude. The Montauk had it motor mounted very high, the Sport 15 had it motor mounted in the old fashioned all-the-way-down position.
The SST did better on the Sport 15, the Stiletto did better on the Montauk. To realize all the benefits of the Stiletto Advantage, the motor must be raised.
What you are describing as cavitation is most likely ventilation. You are SUPPOSED to experience ventilation during the hole shot; that is what the vent holes are for.
Since most Whaler owners are tournament bass fisherman, the ultimate hole shot is not that important and thus vented propeller on Whalers are not hugely beneficial. For waterskiers and marginally powered large boats with four strokes, the vented props can make a big difference.
Remember, vent holes are ONLY for improving acceleration. They can do nothing for top speed or cruise speed. For the most part small vent holes do no harm either so I just ignore them but they can be plugged with silicone caulk if desired.
There is no reason to put a four blade prop on your boat.
Dave at Lockemans is wrong about the motor height. Raise it and see.
Tohsgib posted 08-05-2011 10:44 AM ET (US)
My Stiletto has the vent holes but with a big load she would ventilate at cruise at say 4000-4200 and slowed me down to about 22mph. I filled in the holes with epoxy & kitty hair and holeshot is slightly slower but she holds at cruise no matter the load and 4000-4200 is about 25mph.
Jeff posted 08-07-2011 03:57 PM ET (US)
Tom,
Dave never said "it would not work." He was surprised that I was experiencing this problem after going up one hole. He though I would have been fine there, or even one higher. In our conversion the old gearcase design being a limiting factor developed as a possible theory on what may inducing my problem. I have not been able to run the boat with someone else at the helm allowing me to look over the transom and see how the water is flowing around the lower unit and where the anti ventilation plate is in that flow.
I do understand that cavitation allows the prop to spin up faster and get on plane. Complete loss of grip and having to back way off the throttle and roll power back on is not normal.
In the end, after looking at the way the mounting holes are drilled in the transom I may not be able to move the motor up any more without adding new holes. I have the old external mounted tilt unit on this motor and when it attaches to the motor bracket, it blocks full use of the bottom slot in the motor bracket.
Waterwonderland posted 08-07-2011 04:31 PM ET (US)
Now if you are looking for a volunteer helmsman/spotter, look no further...
Eric
Tom W Clark posted 08-08-2011 12:45 PM ET (US)
Again, what you are experiencing is ventilation not cavitation. I agree it is not normal for you to be experiencing it, but I do not think the older gearcase design is the culprit. I strongly suspect the propeller and motor mounting height is the problem.
The gearcase design from 1974 differs from today's designs in only very small ways. The biggest difference is the swept skeg that OMC introduced c. 1978. It provided a bit more "castor" and stability to the outboard's steering.
The AV plate is a little more substantial on the older design as well, but hydrodynamically, there is not enough difference to be affecting the motor mounting as much as you may seem to think.
You can measure the height of the AV pate above the keel to determine if the 1974 motors has a substantially shorter midsection, but I am sure it does not.
Place a straight edge on the keel and extend it back to the motor. With the motor trimmed so the AV plate is parallel to the keel, measure the vertical distance between the two.
At one hole up I would expect it to be just a wee bit above the keel when it should be an inch or two up, if using a good modern stainless steel propeller.
Jeff posted 08-16-2011 09:23 PM ET (US)
Here is a video I shot of the current set up with a wide angle go pro mounted outboard of the transom today.
http://www.youtube.com/watch?v=DCO2INErDUk
Tom W Clark posted 08-18-2011 10:39 AM ET (US)
Nice GoPro video!
As is plain to see, the motor is buried and needs to come up.

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Author	Topic: 17' Newport 1974 85-HP Evinrude: Performance Data for Stainless Propeller Selection
Jeff	posted 05-27-2009 01:40 PM ET (US) This past weekend I was able to finally get the Newport out on some calm water and get some performance numbers. I finally installed a tachometer over the winter and found it to be time to put it to use. I ran the boat on calm water with very light wave action. The air temp was in the low 60's and all that was on the boat was myself and about 16 to 18 gallons of fuel. The was no wind and the all the speeds were measured on a GPS. The motor on the boat is a 1974 85-HP Evinrude Starfilte turning an aluminum OMC 13x19 prop, and I run it trimmed a ways up so the bow is high. Here are the numbers: 2500: 16.3mph 3000: 22.2mph 3500: 28.8mph 4000: 34.5mph 4500: 38.4mph 4650: 39.5mph WOT Though I can not measure the slip it seems as though the prop loses bite after 3,000 to 3,500-RPM, especially when trimmed up like I run. I am looking to invest into a stainless prop and was looking for recommendations on what ones to test. Cheers, Jeff Rohlfing
Tohsgib	posted 05-28-2009 10:00 AM ET (US) 13.25x17 SST will be fine. Your rpms are too low, check tach setting.
Tom W Clark	posted 05-28-2009 10:35 AM ET (US) Jeff -- You don't measure slip, you calculate it using the propeller calculator: http://continuouswave.com/cgi-bin/propcalc.pl 4650 RPM at 39.5 MPH (assuming a 2:1 gear ratio) would suggest the slip is less than 6 percent, which does not seem likely, especially with an aluminum prop and your feeling the prop was slipping more as the trim increased. I agree with Nick, check your tachometer. Would you verify the gear ratio? 40 MPH is not bad for a 35-year-old 85 HP motor, one that is probably mounted too low for modern propellers.
Jeff	posted 05-29-2009 09:04 AM ET (US) Tom, How would I confirm what my gear ratio is? Also, I was told to set the tach on 6 or 12 pulse. Six was way to high so I figured it was 12.
Tom W Clark	posted 05-29-2009 10:17 AM ET (US) The owner's manual for the motor will contain that information. Who "told" you how the set the tach? What kind if tachometer is it? Did it come with installation instructions?
Tohsgib	posted 05-29-2009 11:16 AM ET (US) Actually Tom...dropping to a 17" would get him close to 5200 which is good for that engine.
Jeff	posted 05-29-2009 11:43 AM ET (US) The tach is a Telefex. Dave at Lockeman's who is my mechanic told me that this specific motor will be a 6 or 12 pulse for the teleflex tach. I will dig up the manual at home to find out lower unit ratio.
Peter	posted 05-29-2009 12:16 PM ET (US) It was 2:1 out of the factory in 1974.
Jeff	posted 05-29-2009 12:20 PM ET (US) Thanks Peter.
Peter	posted 05-29-2009 12:51 PM ET (US) Your reported performance numbers match up with 2:1 too.
Tom W Clark	posted 05-29-2009 01:10 PM ET (US) I agree the 13-1/4" x 17" SST was the prop to use on the OMC 85/90 HP motors, but if Jeff is only seeing 4650 RPM now with a 19" pitch prop then the drop to a 17" is not going to get him much over 5000 RPM and that motor redlines at 5500 RPM. Yes, the motor is old but I want to make sure the tach is reading correctly. Is it possible the existing prop has been worked on with more pitch added?
Tohsgib	posted 05-29-2009 01:46 PM ET (US) Ya never know! I would buy Blackducks alum for $40 and see.
L H G	posted 05-29-2009 02:04 PM ET (US) That engine is performing very close to what many have reported with a new 90 E-tec. So for 5 hp less, and powerhead rated no less, it's doing quite well. Aren't most of the E-tecs running cupped 15" pitch on the 17' hulls?
Tom W Clark	posted 05-29-2009 02:43 PM ET (US) The E-TEC 90 will usually push a Montauk to 42-44 MPH. 15" Stiletto Advantage or 17" OMC/BRP SST/Viper is the usual prop on the 16'-7" models with the E-TEC 90.
Buckda	posted 05-29-2009 03:00 PM ET (US) "Uncertainty...." whispered the serpent. "Surely you can't go that fast with a new E-TEC." "No indeed. If you powered with a 115 HP 90 HP Optimax, surely you would see the low to mid 50's." ....... Jeez...it's like playing that old arcade game "Whack-a-mole". You never know when it'll pop up, but you gotta be quick with the stick.....
Jeff	posted 05-29-2009 10:11 PM ET (US) I found the manual and it recommends the wide open throttle rpm range of 4500 - 5500. It also states in the next sentence that the motor should reach 5000 - 5500 for peak power. I believe I have a spare 13.25 x 17 aluminum OMC prop that came with the boat that I will install on the motor and report what I get. I still can not find any concrete proof on the pulse setting with this motor and tach combination.
Peter	posted 05-29-2009 10:41 PM ET (US) Here, instead of Whack-a-Mole, we play Whack-a-Troll. ;) The 1974 85 Evinrude had a 92 cubic inch displacement. In 1979 they bumped the displacement of the 85 up to 99 cubic inches and in 1981 the 85 and 100 HP models were consolidated into a 90.
L H G	posted 05-30-2009 02:22 AM ET (US) Way back in 1971, the Lake George (NY) Park Commission cops used Nausets with 135 Evinrudes on them as their patrol boats. Those V-4 suckers would absolutely smoke my Nauset with 6 cylinder Merc 150 Tower on it. Great engine.
brisboats	posted 05-30-2009 09:41 AM ET (US) ^^^Thanks for that Larry, I recently sold a member here a very very nice OMC 135 hp and I think he really came by to look at my Mercury inlines. Jeff, Those are great numbers right out of the gate. Running a manual trim 1976 V-4 85hp on my heavier commercial Montauk I could not do nearly as well. Brian
Moby Dick	posted 05-30-2009 10:21 PM ET (US) Jeff.......I hit 41 mph with 2 people (400 lbs) on board with my 1979 Johnson 100HP. It is a 13 1/4 x 17 alum and this it at 5,100 rpm. I was told if I went to a stainless to go with a 16. I question if a 85 HP will turn a 13 1/4 X 17 stainless. Rich
Tohsgib	posted 06-01-2009 11:18 AM ET (US) 1971 was still a 125hp OMC, 1973-76 they made the 135's. 1977 it went to a 140 until 1984.
Jeff	posted 06-01-2009 09:19 PM ET (US) Well, I dug around this past weekend and found the other prop. Turns out it is a 13 1/4 x 17 OMC after all. I broke out the file and cleaned up some nicks on the blades and plan to run it this weekend on a local lake. I will take down numbers and report back. I guess all in all I am happy with the cruising numbers but, expected more at the top end. While I do run at wide open throttle now and then it is not for long periods of time. The thing is our 1984 Montauk with the 1984 Mariner (Merc) 90 Tower would push that hull to 48 - 49 on a standard Quicksilver aluminum prop (I believe it was a 13 x 19). So, that was my bench mark going into this with the Newport. It is all trade off's though. This OMC V4 starts and idles much better with less smoke than the Mariner. Brian, Funny Jim commented about the tower you have sitting around when I saw him last weekend. He said he looked at when he bought your 135. I ended up giving him a OEM tilt unit for that motor after he got it.
L H G	posted 06-01-2009 11:34 PM ET (US) Jeff - Comparing an old powerhead rated 92 inch V-4 with a six-cylinder 100 inch Merc 90, propshaft rated, is like apples and oranges! Much greater than the "decal HP" would indicate. To hold that "tower" down to only 90 HP, they had to hold the RPM's down to 5000 max with smaller carb jets and timing changes. With the possible exception of the later 2-stroke Merc 90 3 cylinder, which Clark Roberts here has indicated can also do 48 on a Montauk, there is no other modern 90 that can accomplish that speed on a Montauk as far as I know.
brisboats	posted 06-02-2009 01:25 PM ET (US) Jeff, Thanks that will be a great compliment to Jim's 135hp. Are you running power trim on the Newport? Brian
Jeff	posted 06-02-2009 02:36 PM ET (US) Brian, Yes I have the OEM external mount power trim. This is the same unit as what I gave Dunlap. The one I gave him needs the seals replaced on the rams but, I was unable to find anyone to do it. Do you know of anyone? http://link.brightcove.com/services/player/ bcpid22879159001?bclid=22378947001&bctid=24827451001p
Jeff	posted 06-02-2009 02:43 PM ET (US) Sorry, I missed up my work links with my other stuff.... Here are is the image http://smg.photobucket.com/albums/v427/jeff_rohlfing/ 76%20Newport%20Near%20Complete/?action=view¤t=DSC_3639.jpg
brisboats	posted 06-02-2009 10:28 PM ET (US) Jeff, I don't know anyone off hand but will ask Brian at Fairwinds when I see him later this week. Fairwinds is our local Lockeman's. Interested to see if you can dial her in a bit more and hope you do but I think 39mph is darn respectable even if it is a bit shy of the all mighty inline. Brian
Tom W Clark	posted 06-05-2009 10:50 PM ET (US) Jeff, Have you run the old OMC 17" aluminum yet?
Jeff	posted 06-06-2009 08:31 PM ET (US) Tom, I just got back in from running it today. Here are the numbers. Conditions were about the same. 13 1/4" x 17 OMC Aluminum 2000: 7.6mph 2500: 9.2mph 3000: 15.9mph 3500: 22.1mph 4000: 26.7mph 4500: 30.1mph 5000: 33.6mph 5400: 35.3mph WOT
Tohsgib	posted 06-07-2009 10:41 AM ET (US) Again I think with the 17" SST you should see 52-5300 and closer to 38-39mph.
Jeff	posted 06-01-2010 02:22 PM ET (US) This past weekend I was able to run another prop. While I never did record all of the RPM ranges I did see improved results. The prop was an OMC SST 13 3/8" x 17 which reached a WOT of 5150 RPM and a GPS reading of 40.2mph. Water conditions had light wave action with air temps in the upper 70's. I think this is the right prop selection especially after I move the motor up one hole. I am still having a lot of water coming up the cavitation plate.
Tohsgib	posted 06-01-2010 02:53 PM ET (US) That prop will be good.
Tom W Clark	posted 06-01-2010 03:01 PM ET (US) Nice. I does show what a big difference a switch from aluminum to stainless steel can make. I agree, the 17" OMC SST is a good prop and a good fit. You will not see the full advantage of it until you raise the motor.
Teak Oil	posted 06-01-2010 10:05 PM ET (US) Those are good numbers Jeff, 42mph might be attainable with some more engine height. I can get 46 mph routinely alone with my 90 'Rude, but its 10 years newer and has an adjustable jackplate. With passengers I usually get 43.5-44mph.
brisboats	posted 06-02-2010 10:38 AM ET (US) Looking good Jeff! My eyes maybe failing but did I read above that LHG admits an OMC 135hp V-4 smoked his Mercury 150hp inline? Brian
Jeff	posted 09-06-2010 10:20 PM ET (US) Today I was finally able to log a full set of numbers on the 1976 Newport and the 85hp Evinrude Starflite turning the OMC SST 13 3/8" x 17. Air temps were in the low 70's and so where the water temps. Water conditions were a light chop and slight breeze. Boat had 16 - 17 Gallons of fuel. 2000: 8.5mph 2500: 13.8mph 3000: 20.5mph 3500: 25.6mph 4000: 30.8mph 4500: 34.7mph 5000: 38.4mph 5175: 40.3mph (WOT trimmed all the way out) At this point I am very happy with this set up...
Tom W Clark	posted 09-12-2010 11:16 AM ET (US) Yes, that is very good performance for a 36 year old 85 HP outboard motor. It will improve even more once you raise the motor a hole.
64nauset	posted 09-15-2010 09:50 AM ET (US) The tech guy at Stiletto said to expect about a 100rpm gain at WOT for each hole the motor is raised up. I have not tested that theory.
Tom W Clark	posted 09-20-2010 08:29 PM ET (US) On the typical Whaler, only 100 RPM is a rather conservative estimate. Most will see more
Jeff	posted 07-01-2011 10:42 PM ET (US) I raised the motor up one hole this week as it was mounted all the way down. This evening I headed out alone for the first runs with the motor raised. My test numbers where exactly the same however, the prop was cavitating FAR more during the hole shot, on plane acceleration and in the turns. I would prefer not to move the motor back down. Is there a recommendation on a better prop to cure this cavitation?
dgoodhue	posted 07-02-2011 06:02 AM ET (US) I don't have experience with classsic 16/17 hulls, but I am surprise one hole has cavitation issues. Is the motor trimmed out at all? A Stiletto 13 1/4" x 15P will have the same RPM range as your 13 3/8" x 17P SST and tolerate one hole higher mounting,
Tom W Clark	posted 07-02-2011 11:26 AM ET (US) There is no way that SST should be losing grip at only one hole up. Even at that motor mounting height a cheap aluminum prop will grip without any trouble. If you go the 13-1/4" x 15" Stiletto Advantage 4.25 or Turbo 1, you can mount the motor as high as it will go with no loss of grip.
Tohsgib	posted 07-04-2011 01:06 AM ET (US) I agree with Tom that 3/4 of an inch higher should not have any effect on performance like you posted. My engine is close to 5" higher and with a Stiletto prop you would NEVER know.
Jeff	posted 08-05-2011 03:01 AM ET (US) Over Vacation 3 weeks ago I was able to borrow a 13 7/8"x17' Viper with vent holes from Lockeman's hardware and boats. Due to some circumstances I was unable to get full data numbers but, I was able to test the prop. I found that this prop was much larger in mass than my current prop and engaged into gear with a solid thud. Planing was much improved and I was able to planing with out much of any cavitation so long as rolled on the power. If I when to WOT hard it would slip while coming out of the hole. I was able to hold grip in all turning situations even if I had the motor trimmed out and was on a hard turn in. The current SST blows out in most all turns. No matter how I had the motor trimmed I was getting 39.5 - 39.9 on the GPS with the Viper. On a side note I was able to see 40.7 this past weekend with my current 13 3/8" x 17" SST once it finally stopped cavititing and held grip. All in all the Viper was a better option to the current 13 3/8" x 17" SST I have. Though I would still like to try some other props before settling. I hope to try a non-ventilated 13 7/8"x17' Viper as Dave at Lockemans stated that might be the better option and I might not experience the cavitation while planing with that prop. I would also like to try a Stiletto Advantage if I can round on up. Is there any reason to consider a 4 blade prop? As for the mounting height. I think I may disagree with the common convention of you can keep going much higher if at all with my motor. In speaking with Dave at Lockemans he said that the old old style lower unit design I have on this 1974 may not tolerate the elevated running height like later designs do.
Tom W Clark	posted 08-05-2011 10:40 AM ET (US) Jeff -- Your motor is only one hole up now and it can go up one or two more holes with the Stiletto Advantage. I have seen this again and again, the OMC/BRP props, while good, will not tolerate as high a motor mounting height. Some years ago, Rob Schmidt and I tested an SST against a Stiletto Advantage on both a Montauk with an Evinrude and a Sport 15 with an Evinrude. The Montauk had it motor mounted very high, the Sport 15 had it motor mounted in the old fashioned all-the-way-down position. The SST did better on the Sport 15, the Stiletto did better on the Montauk. To realize all the benefits of the Stiletto Advantage, the motor must be raised. What you are describing as cavitation is most likely ventilation. You are SUPPOSED to experience ventilation during the hole shot; that is what the vent holes are for. Since most Whaler owners are tournament bass fisherman, the ultimate hole shot is not that important and thus vented propeller on Whalers are not hugely beneficial. For waterskiers and marginally powered large boats with four strokes, the vented props can make a big difference. Remember, vent holes are ONLY for improving acceleration. They can do nothing for top speed or cruise speed. For the most part small vent holes do no harm either so I just ignore them but they can be plugged with silicone caulk if desired. There is no reason to put a four blade prop on your boat. Dave at Lockemans is wrong about the motor height. Raise it and see.
Tohsgib	posted 08-05-2011 10:44 AM ET (US) My Stiletto has the vent holes but with a big load she would ventilate at cruise at say 4000-4200 and slowed me down to about 22mph. I filled in the holes with epoxy & kitty hair and holeshot is slightly slower but she holds at cruise no matter the load and 4000-4200 is about 25mph.
Jeff	posted 08-07-2011 03:57 PM ET (US) Tom, Dave never said "it would not work." He was surprised that I was experiencing this problem after going up one hole. He though I would have been fine there, or even one higher. In our conversion the old gearcase design being a limiting factor developed as a possible theory on what may inducing my problem. I have not been able to run the boat with someone else at the helm allowing me to look over the transom and see how the water is flowing around the lower unit and where the anti ventilation plate is in that flow. I do understand that cavitation allows the prop to spin up faster and get on plane. Complete loss of grip and having to back way off the throttle and roll power back on is not normal. In the end, after looking at the way the mounting holes are drilled in the transom I may not be able to move the motor up any more without adding new holes. I have the old external mounted tilt unit on this motor and when it attaches to the motor bracket, it blocks full use of the bottom slot in the motor bracket.
Waterwonderland	posted 08-07-2011 04:31 PM ET (US) Now if you are looking for a volunteer helmsman/spotter, look no further... Eric
Tom W Clark	posted 08-08-2011 12:45 PM ET (US) Again, what you are experiencing is ventilation not cavitation. I agree it is not normal for you to be experiencing it, but I do not think the older gearcase design is the culprit. I strongly suspect the propeller and motor mounting height is the problem. The gearcase design from 1974 differs from today's designs in only very small ways. The biggest difference is the swept skeg that OMC introduced c. 1978. It provided a bit more "castor" and stability to the outboard's steering. The AV plate is a little more substantial on the older design as well, but hydrodynamically, there is not enough difference to be affecting the motor mounting as much as you may seem to think. You can measure the height of the AV pate above the keel to determine if the 1974 motors has a substantially shorter midsection, but I am sure it does not. Place a straight edge on the keel and extend it back to the motor. With the motor trimmed so the AV plate is parallel to the keel, measure the vertical distance between the two. At one hole up I would expect it to be just a wee bit above the keel when it should be an inch or two up, if using a good modern stainless steel propeller.
Jeff	posted 08-16-2011 09:23 PM ET (US) Here is a video I shot of the current set up with a wide angle go pro mounted outboard of the transom today. http://www.youtube.com/watch?v=DCO2INErDUk
Tom W Clark	posted 08-18-2011 10:39 AM ET (US) Nice GoPro video! As is plain to see, the motor is buried and needs to come up.