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Author Topic:   New Suzuki 70 prop?
placerville posted 12-03-2003 09:08 PM ET (US)   Profile for placerville   Send Email to placerville  
I just received my new 70hp Suzuki from
Bayracer marine. It came with 13.25 X 16"
stainless prop. Is this going to be too
small a pitch for my Montauk? I use it for
open ocean cruising. Don't ski. Thanks
Estero posted 12-04-2003 12:43 AM ET (US)     Profile for Estero  Send Email to Estero     
I've had the same thoughts, I'm one of the others that ran with the great info that Todd developed and bought that same engine to repower my '82 Montauk, and the props that were first suggested by the dealer were even lower pitches (14 and 15 inches). I settled on the 13.25x16 stainless, but after more consideration and research I expect that once I get through the initial break-in on the motor I'm going to find myself underpropped and will have to try to swap for a higher pitch. Time will tell...

Placerville, I have a few other other questions that I would like to email to you off-board if you don't mind. Between work, family and the holidays, my motor won't see the water until 2004, so if you get yours in sooner, I'd be interested to hear your thoughts.

Tim

David Jenkins posted 12-04-2003 08:43 AM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
I use a 13.25x16 stainless on my Evinrude (Suzuki) 4-stroke 70 hp motor and it works great. With a light load, the prop will allow the engine to turn more than 5600 RPM but I that is not a problem as I rarely run the engine higher than 4200 RPM. With a heavy load, I am at 5600 RPM at full throttle.

I also have a 13.25x19 stainless and with the boat completely empty of fuel and gear it will also get 5600 RPM, but with the boat loaded down to full capacity it will only allow the engine to turn 4800 RPM. Since I am almost always fully loaded with gear and fuel, I opted for the smaller prop.

My engine is on a 1977 15' Whaler with five custom chairs mounted to 5/4" mahogany, a 42-gallon Pate fuel tank, and an 8' stainless Bimini. I imagine that my boat weighs as much as the average 16/17.

JBCornwell posted 12-04-2003 09:38 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Hi, Placerville.

I started testing with a 17" prop on my Suzuki DF70 powered Montauk. With a light load it would exceed 6,000rpm, so I went to an 18" SS and got 5800 rpm lightly loaded.

I later added weight to the bow (big Genesis) and picked up another fishing buddy (3rd generation). The 18" would then only get me to 5,000rpm WOT.

I went back to the 17" and got the best all-round performance for the way I load and use my boat.

My dealer also wanted to equip me with a 15", but I insisted on sea trials and ended up with the 18" (which is now on Bigshot's Montauk). I think many dealers expect a 17 foot boat to be a lot heavier than a Montauk.

Based on all that, I suggest you start with a 17" pitch.

Red sky at night. . .
JB

David Jenkins posted 12-04-2003 10:46 AM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
From my experience and JB's experience, it sounds like the pitch you need can be determined my how much load you expect to carry. If you plan on running with a light load (1-2 people on board, 12 gallons of fuel, 1 battery), then go with the 13.25x18 prop for the 16/17' Whaler (or the 13.25x19 for the 15' Whaler).

If you plan on sometimes carrying 3-4 passengers and 24 gallons of fuel and/or camping gear, or if you want to pull something behind your boat, go with the 13.25x17.

If you plan on loading down the boat to its maximum capacity, go with the 13.25x16.

As Sal and others have explained before, if you have too small of a pitch then you run the risk of running the RPMs over 5600 RPM and damaging your engine. And if you stop at 5600 RPM and you are not at dead rack, then your engine is not giving its optimum performance (it could go faster if you had installed a prop with a bigger pitch).

On the other hand, if you have too much pitch and your Wide Open Throttle (WOT) is only 4800 or 5000 RPM, then you are doing serious damage to your engine at all speeds.

Yikes! I'm not willing to take that risk.

So, if you are just going to have one prop and if you ever plan to carry six passengers and lots of fuel and gear, stay with the 13.25x16.

Bigshot posted 12-04-2003 03:42 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I have run 8 different props on mine and I am the happiest with JB's. With the heavier weight of my Newtauk over the Montauk I spin about 5700WOT. Here are what I had in the past on my 89 Montauk with bottom paint and a jackplate. This is with 2 people and a full 27 Pate tank running in brackish water. (FYI-OMC props fit suzuki)

14x17 Alum OMC prop: 4000 rpm=22.5mph, 4500=27, 5000=30, 5800=35.

13x19 suzuki alum: 4000=29, 4500=34, 5450WOT=39.3

13 3/8x17 OMC SST; 4000=24, 4500=28.4, 5800=37

I have not GPS'd the 18" yet but at 4000 I am doing about 27mph and wot is about 5700rpm. The 13x19 looks enticing but put 3 people in it and you will barely get 5k wot. If you have a new 16" send it back for the 18Alum or 17-18"SS depending on load you run. Light loads get the 18" stainless.

Bigshot posted 12-04-2003 03:45 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I ama also assuming that you know WOT is 52-5800 on the 70hp. If you always run just 1 or 2 people, the 19" is within guidelines but she will dog with 4 people.
placerville posted 12-04-2003 08:25 PM ET (US)     Profile for placerville  Send Email to placerville     
Wow! Thanks for are that info. I do often run
with a heavy load, three people and 30 gallons of
gas. So I think I'll keep the 16" SS and get a second
18" aluminum when I'm light.
nevada posted 12-05-2003 11:42 AM ET (US)     Profile for nevada  Send Email to nevada     
I run a Suzuki 13 ľ x 8 SS prop on my DF70 with a four-inch bracket pushing a 1979 Montauk. I have less than twenty hours on it so I donít have any solid performance numbers to report yet. But so far it has seen 34 mph GPS @ 5400 WOT for a short spell. I do hope to see Nickís reported 39 mph when she is fully broken in.

Joe

nevada posted 12-05-2003 11:44 AM ET (US)     Profile for nevada  Send Email to nevada     
Correction that is a 13 1/4 x 18 SS prob.
nevada posted 12-05-2003 11:58 AM ET (US)     Profile for nevada  Send Email to nevada     
sorry, No coffee yet prop.
David Jenkins posted 12-05-2003 12:09 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
The 4" setback on your jackplate may be a significant factor. When I had the 13.25x19 SS prop on my engine I was using a similar CMC jackplate (I got rid of the jackplate because it made the boat too back-heavy). The next time out I only got 4800 RPM at WOT. I assumed that it was because I had a full tank of gas and had a couple of buddies on board, but the absence of the jackplate may have kept me from getting a higher RPM at WOT.

So if you are using a jackplate, then you may be able to use a prop with more pitch that if you were not using the jackplate.

If you do not use a jackplate and you sometimes carry maximum load of 7 people or that weight equivalent in fuel and gear, you might want to go with the 13.25x16.

If you do use a jackplate with 4" or more in setback and you never load the boat down to its maximum weight capacity: you might want to choose the 13.25x17 or 13.25x18.

I would rather have my engine last a long time than try to make the boat go as fast as possible. That is why I choose the 13.25x16: I want to make sure that I never put unncessary strain on the engine due to it being overpropped. So far, so good: my year 2000 engine has 1600 hours on it and it runs like new.

Bigshot posted 12-05-2003 03:46 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Try it Placerville but I think a 16 will be too small. I could get my 17" to over rev if I really trimmed the snot out of it with just me. 3 people and a full pate is not a heavy load. My speeds posted are with 2 people and a full Pate(27gal) so you won't be far off. I think with the 16" you will over rev it as well. I also think your cruise will be slow at about 20+ at 4k which is then stressing the engine in a different way. I would try the 18" and if too big with load(I doubt) you can always try a 17" OMC which are VERY popular used on E-Bay for about $70-120 in SS. Double cupping will drop you about 200rpm as well.

In order to get the speeds I am getting I am trimming the snot out of it. I am NOT breaking loose but just at the cusp. I am throwing about a 6' tall rooster tail behind me as I go. I just moved it up another 1.5" on the jackplate and I am no longer running bottom paint but my Newtauk is about 100lbs heavier than my Montauk so I will post my GPS speeds hopefully soon.

PS I did the Kice island trip with 3 people, full gas, 2 tents, 2 coolers(loaded), and all assorted camping gear. Boat was sitting a tad low in the water. She would hit just over 5k WOT. Therefore I still think the 18" is the best all around prop because even if you hit 5200 WOT loaded down, you are still in spec for WOT operation.

nevada posted 12-05-2003 04:18 PM ET (US)     Profile for nevada  Send Email to nevada     
Nick when you say 'I am NOT breaking loose but just at the cusp" are you refering to porposing?

Joe

David Jenkins posted 12-05-2003 06:25 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Well, I did not realize that 5200 RPM was still in spec for WOT operation. Sal scared me in another thread when he said that if I could not get 5600 WOT and I took a long trip, then I would put such a strain on my engine that it might ruin it, even if I ran the engine at a much lower RPM.

I mostly use my boat for trips of about 200 miles. And on these trips I usually have four people on board, a 42-gallon fuel tank, a full ice chest, two tents, lots of water, and various other items--I am loaded to the max. With the 16 prop, I can still get 5600 RPM loaded this way. I am sure that it would over-rev if I was lightly loaded, but I have never tried so the only problem that I see is that I may not be going as fast as I might otherwise travel if I were using a prop with a larger pitch. RIght?

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