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Author Topic:   OMC 88, 90, 115
MikeG posted 03-16-2000 11:47 PM ET (US)   Profile for MikeG   Send Email to MikeG  
I have a '88 Whaler Montauk. It has an 88hp Evinrude SPL engine. The boat has a very powerful start and will go about 36-38mph with almost any load. I was expecting more speed however(feels kind of slow on flat water). It has an aluminum prop which may be part of the problem, but it does rev to 5500rpm at WOT. Does anyone know the differences between the 88SPL, 90hp and 115hp OMC engines? I have a 1988 88SPL as was wondering where the 115hp get its extra power. They appear to be the same engine, case, weight, cyl (bore and stroke). I know my SPL does not have the VRO oil mixer, but what else is different? Carbs? Exhaust? I would be interested to hear if anyone has experiences with these engines and knows how to extract more power without heavy modifications. Also if anyone thinks a prop change could help to get more speed without running the engine hard. Is 45mph out of a Montauk a myth? :-)


lhg posted 03-17-2000 01:03 PM ET (US)     Profile for lhg    
I am not particularly knowledgeable about OMC engines, but I do know that those "odd numbered" HP engines were their economy models, designed to compete with the Mercury Force brand. A lot of OMC dealers sold these for competitive pricing on their boat/motor/trailer packages. I would image that the "standard numbered" HP models would be a lot stronger. A friend had a 1983 17' Montauk, with a 90HP Merc in-line six, and it would run about 47MPH with a 19" pitch prop. I also had a 1971 16' Nauset, with a Merc 115 in-line six, and it would run about 52MPH with a 21" prop. I do believe, however, that the 16' hull was faster (and a little lighter) than the 17' hull introduced in 1975/1976.
Walt Steffens posted 03-17-2000 03:39 PM ET (US)     Profile for Walt Steffens  Send Email to Walt Steffens     
Mike: Although I am not an OMC mechanic I have owned several OMC V4's. In general the V4 engines of this era (80's) were basically the same. Usually they came in three HP ratings something on the line of 90,110,140. The lowest HP of the year series was the most conservitavly built. In my case I had a pair of 110 hp engines on a 22 revenge (84 model). I did some investigation on the and found that it was not an easy bolt on change. Although the engines shared common blocks and cranks and sometimes even rods, the HP increases were achieved by changing Carbs & Mounting Plates including reed valves, exhaust chambers (located on the aft of the engine between the V's) and also pistons and sometimes cyl heads. Also in my case the block would have had to be bored out to a larger piston diameter to get the diffrence in CU IN between a 110 & a 140 HP engine. My experience showed that unless I had a popped power head the parts and machine work (done at a shop specializing in outboard blocks) wasn't worth the expenditure, even if I was the one twisting the wrenches.

A Stainless Steel double cupped prop might get you more top end as its blades won't flex as much and the aluminum one, however from my experience once you pass about 40 mph in that hull (I had a 79 17' Newport) the water starts getting really hard and the boat starts to porpose. This can be controlled with the tilt & trim however as you get to the point where there is only about the last 18" of the hull and the cavitation plate in the water it doesn't feel all that stable to me as the steering gets more touchy and any looseness in the steering system shows up. My 25 Revenge WT w/twin 150's is a true 50 MPH + ride (chedked with a GPS) although I find the same things with it, its just not fun or comfortable. At that sort of speed a split second of in-attention and you can be in real trouble. My suggestion is that if you do a lot of WOT HS running make sure that you utilize the kill switch lanyard this will stop the boat if your thown overboard and also keep the boat from circling and running you down. Hope this helps you.

peter welch posted 05-08-2000 09:20 PM ET (US)     Profile for peter welch  Send Email to peter welch     
45 mph is not a myth! I have a 1966 hull that started out as a Currituck but was restored to be as close to a center console Montauk as I could make it. I have an 88 SPL Evinrude with a stainless prop and 45 is no problem with my wife and I aboard in glass calm water. 45 is pretty exciting! The hull does start to porpoise but it is mangeable. We only do it in short bursts, however, because there is a whole lot of shaking going on at that speed. Its just not worth it to shake loose a bimini fitting etc. The boat is much smoother at about 35 mph.
MikeG posted 05-10-2000 12:27 AM ET (US)     Profile for MikeG  Send Email to MikeG     
What type of prop do you use (make, pitch, diameter)? I have what appears to be the standard OMC aluminum prop. I had my Montauk out this weekend and was clocking a consistent 37.5mph (GPS) with two people in a very slight chop (35mph with 5 people) @5500rpm. I believe the older hulls may be a little faster. My boat and engine are 1988. Do you have power trim or play with the trim pin settings at all? I am considering refitting the motor with a SS prop and keeping the aluminum as a spare. I would like to keep the low speed grunt and improve the top end. Any thoughts on prop selection would be appreciated.
Clark Roberts posted 05-10-2000 07:02 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Mike, I have owned several (maybe 10) V-4, 99 cubic inch OMC outboards in horsepowers from 85 up to 140 and had best luck with the factory stainless prop (of correct pitch)! These were, and still are I think) , called SST (stainless steel, teflon). The blade design and thickness seemed to allow max engine performance. I tried other styles and trick props but always came back to the SST! Beware of high rake specialty props, the ones designed for bow lifting on bass boats! Good prop hunting! Clark
Bill D posted 05-11-2000 08:07 AM ET (US)     Profile for Bill D  Send Email to Bill D     
Mike, I agree with Clark. I tried both the
SST (black/teflon/stainless) and Raker (polished stainles) OMC props and the SST preformed the best(same pitch). My 87 Montauk
w/90hp OMC would run right at 49mph and this Montauk was loaded. I had the rear "striper"
deck, dual batt's, 27gal under seat gas tank,
so I had a lot of weight in the back. I borrowed a trick from my bassboat days and put a jackplate on. This allowed me to adjust
the engine height has high as possible without causing the prop to blowout. I could
not trim all the way out with getting a lottle porposing, but it was real close to being all the way out. If I remember correctly I was running a 19 pitch SST and the rpm's were 5700 at wot.
Ed Doran posted 05-13-2000 10:52 PM ET (US)     Profile for Ed Doran  Send Email to Ed Doran     
I just bought a 1985 Montauk. I can't tell you how much I have learned by reading in the forum. Thanks and keep talking
MikeG posted 05-15-2000 11:21 AM ET (US)     Profile for MikeG  Send Email to MikeG     
OK, I am ready to buy a new SST prop. I was looking at the prop on my boat and saw it was a 13.75 X 15. No wonder I was getting such a powerful start with a low top end. I probably could have pushed a barge with such a shallow pitch! Oh well, I'm still learning. Anyway, what is the best diameter and pitch for a Montauk w/ an 88SPL? I was thinking a 13X19 OMC SST. I run the boat with anywhere from 2-6 people and sometimes tow a skier or a tube. I would like to be able to cruise at 35mph w/o running the engine too hard and improve my mpg of fuel. Running in the 40's on flat water would be fun too! Also, I could use a few pointers on the best way to buy a prop. Will most dealers let me try a number of different props at one time so that I can compare? An SST looks like it will cost $400+, does anyone know where I could get a good deal on one? I live in the Philadelphia area. What is the story with reconditioned SS props? Are they inferior to new props? I am planning to hold on to the old aluminum prop b/c there will be days when I will want to have the extra grunt vs. high speed. I would be interested in hearing everyones thoughts.
Bill D posted 05-16-2000 10:30 AM ET (US)     Profile for Bill D  Send Email to Bill D     
Mike, What is the factory approved WOT rpm range on your 88SPL? Going from a 15 to a 19
pitch may reduce your rpms below approved
level. It seems your 15 is turning about the
right rpm's. You asked someone about trim/tilt, does your motor have power t/t?
Also, how high is your motor mounted (how much of the lower unit is below the bottom)?
MikeG posted 05-16-2000 11:50 AM ET (US)     Profile for MikeG  Send Email to MikeG     

The 88SPL is rated for 4500-5500rpm at WOT. I am not sure exactly how it works, but it seems that there is a stop set on the throttle cable near the carbeurator that is keeping me from over-revving the engine. A few people with similar engines on Montauks are apparently using 19" pitch and still turning 5500rpm. That might be because the 19" has a smaller diameter than the 15" (13 v. 13.75) My engine does not sound burdened by running it at WOT with the 15" and it gets to its top speed in just a few seconds. I would like to test the prop before I buy it, however. My engine does not have t/t but it can be added. Apparently I can buy a refurbished t/t kit for $450 (one thing at a time I guess... I need new cushions $400+, a new prop $400+, and I just installed a Humminbird 3D d/s $400). As for the engine height, the cavitation plate is at the same level as the bottom of the hull. I'm afraid to raise it any higher. I'm concerned that I'm running about 10mph slower than similar Montauks and I think a prop change could make up some of that difference. I'd be suprised if 2hp and a VRO will account for the difference. Thanks for the input.

Bill D posted 05-16-2000 12:31 PM ET (US)     Profile for Bill D  Send Email to Bill D     
I think my 90hp had an approved rpm of 5000-6000. Your 88SPL is operating at the top of the rpm range for WOT. Sounds like your mounting height is correct. A 19 pitch prop
probably will be in the lower half of your approved rpm at WOT. Not having Power T/T, probably keeps you from running any faster,
but a 15 pitch prop would probably over-rev.
I know what you mean about $'s... There is
always something else I want to add to my Whaler. Good thing the Admiral(wife) keeps tabs on my spending. If it were me and I wanted more out of your setup, I'd added T/T
first and work on the prop after that, even
if I had use a used alum. 17 or 19. Without
T/T you have to set your trim as a trade off
between holeshot and optimum top end. Anyway
thats just my opinion....
TRIDENT posted 06-01-2000 06:33 PM ET (US)     Profile for TRIDENT  Send Email to TRIDENT     
My 1981 Montauk with Mercury 115 runs 47 mph (GPS). I think the power tilt/trim will give you the most bang for your buck. My fishing buddy just replaced his 88 HP Evinrude and has 3 or 4 nice stainless prop for it that he wants to sell. He may even have the exact one you need and give you a really good deal. We are fishing together this weekend. If you send me an e-mail I will pass it along to him and he will let you know what exactly he has/price/etc. next week. Happy Whalin'

whalernut posted 06-01-2000 09:25 PM ET (US)     Profile for whalernut  Send Email to whalernut     
Mike, I have a 73` `16 Currituck with the old hull design, it has a 75` 85h.p. Johnson with no power tilt/trim. I do not have any gauges, but the boat simply flies with me or one passenger, to the point it feels like it barely is touching the water. I have a whales tale on the lower unit, so it tracks great and planes fast. Acctually, I am looking to sell/trade the engine for a 60/70h.p. engine because the 85h.p. engine is a little to high strung for trolling. A 60/70h.p. engine would troll slower, better fuel mileage, and lighter on the transom! I also want an outboard with 50/50 mix, I don`t like oil-injection. Power or manual trim isn`t a big deal to me as I fish in deep water in Lake Erie and do no skiing. So you see it is a personal preference when it comes to h.p. on a 16/17 foot hull. It seems most people like the 80-100h.p. range for overall use. Fishing-skiiing-tubing-power for weight. Good luck-JACK.
MikeG posted 06-02-2000 12:05 AM ET (US)     Profile for MikeG  Send Email to MikeG     
Thanks for the responses. I have borrowed 2 props from the local whaler dealer to test... a 13.25 X 17 AL and a 13 X 19 SST. Both look a little worn but hopefully will give me a good idea of which prop I should buy (they wouldn't let me get new ones wet w/o buying them). I'm trying to find a happy balance between ski & tube pulling power and speed. I also push around a wide range of loads from 1-6 people (once carried 7 people, a kayak and camping gear to an island 4 miles out, I love these boats!). Its rained the last few weekends so I haven't seen the water in a while. The weather looks good this weekend so I should have a better idea of what I want by Sunday.

Concerning power T/T, has anyone ever installed one of these themselves? What kind of job could I be getting into? I'm handy enough, but this is my first boat (pictures of installed units could be helpful). The place that sells the T/T units pulls them from scrapped engines, rebuilds and warrants them for about $450 (new $800). This may be a project for next winter (funds are short and I would hate to tie up the boat for a weekend!) Any input would be appreciated.

Trident, I'd be interested to hear about your friends SS props. I'll send you an e-mail later.

Thanks! Mike

lhg posted 05-24-2001 01:20 AM ET (US)     Profile for lhg    
Since so many have OMC V-4's on their Whalers, we should keep this one alive.

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