Repowering with less HP

[porkchop401]

Well my 115 tohatsu TLDI recently locked up , it is on a 2007 Critchfield 18ftcc . The motor weighs 381lbs and is all the weight I want on the boat . I am considering replacing with a 90hp 4 stroke to save the weight and the $$$$$. The boat had power to spare with a quick plane with 2 lard asses and a top speed of 40mph whitch I seldom pushed the boat to (I'm not racing). So my question will a properly pitched 4 stroke 90 hp out board push my boat and what kind of speed can I expect, I would be happy with 30mph and still have decent get up.

 

[b.gagnon]

If you are fine with a loss in performance go for it! A 90hp 4-stroke will be great on gas. Go to the Mercury web site and use the prop finder....It will give you a good idea of how it will perform. The hole shot on a 90hp 4-stroke will not even be close to a 115hp 2-stroke but top end won't be too bad.
The only problem I see is the Re-sale value will suffer quite a bit....

 

[Sea Rider]

If going for a 4 stroke 90HP OB you need a wot water trial lightly loaded prefferably you alone on flat no windy water cond. Check factory wot range with standard delivered prop rpm. Cam maximize pitch to be around or near max wot range. Should have good hole shot with slight less top speed. Once there can throttle throughout the whole throttle rangte with nice performance & fuel comsumption. It's imperative to water test any given prop as most times theory doesn't dial well in the practice.

Happy Boating

 

[porkchop401]

Thanks fellas , does anybody have any experience with a Suzuki 90 ?

 

[steelespike]

While it will probably be a lot more than the Suzuki You should try out a 90 Evinrude Etec,2 stroke Direct injection.320 lbs.
Performance reports boats from 1800 lbs dw. AL 15" prop 34.4 mph and 4.5 sec. to plane, 1100 lb .SS17" 42.2 mph 3.5 sec. to plane.
2050 dw 15" 32 mph 5 sec to plane. There are about 25 reports at the Etec site.

 

[porkchop401]

I appreciate the advice on the etec , my previous outboard was a 4 stroke Yamaha 60 on a 16' bass boat and I absolutely loved the quiet power.

 

[Frank Acampora]

While I don't have experience with a Suzy 90 I do have experience with Zuki 30 3 cylinder four stroke. My partner and I worked on this engine and replaced a piston. We mounted it on a 15-16 foot fiberglass hull and it was surprising. It challenged all that I had been told about 4 stroke engines. Quiet--we could talk with each other at speed, clean, good idle, and PLENTY of pick-up.

If the 90 performs similarly to the 30 you will not be disappointed with performance even though you probably will see a slightly less top speed than from the 115.

My only disappointment was with the design: The previous owner hit a log and trashed the lower unit. He installed a factory new lower and never could get it to run. We Found out that the valve timing chain sprocket was heat shrunk on the crankshaft with no locating keys or set screws. When the P,O hit the log he did move the timing sprocket and until we realized this we could not get the engine to run correctly. Ultimately we needed to ignore the timing marks and set valve timing by the position of the #1 piston. Once valve timing was st the engine ran like a champ.

 

[steelespike]

I appreciate the advice on the etec , my previous outboard was a 4 stroke Yamaha 60 on a 16' bass boat and I absolutely loved the quiet power.

Any motor you decide on you should be there is a servicing dealer close by.

 

[porkchop401]

Any motor you decide on you should be there is a servicing dealer close by.

That is a concern for sure, I have been looking at buying on line but understand dealers really frown on any thing bought on line that could be bought through them.does a outboard have to be installed buy a dealer in order to recieve the warrenty.

 

[fishin98]

Until recently I had a 2000 Bayliner 1802 Capri Cuddy, with a 2000 90HP Merc 2str, I ran a 19P 3 blade prop and a 19P 4 blade. WOT it topped out around 40mph with 2 people on board, 3/4 throttle gave me 30mph....super easy on fuel..You could probably expect similar performance...I have talked with people who have similar sized boats with a 90 4str Merc and are quite pleased. Having a respectable Dealer/Mechanic close by is also a plus.

 

[steelespike]

Any motor you decide on you should be sure there is a servicing dealer close by.

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