18' + 25hp = 13.3 mph

[JohnK]

I got my new (used) boat out on the lake on a calm day with the GPS and was only able to squeeze out a max 13.3 mph. The previous day with a roughly 10mph headwind and 3 adults and 2 small children best speed was only about 9.5mph.

1982 18' Crestliner, 25hp Suzuki, full wood floor, 2 adults 1 child on board and with a slight tail wind 13.3 was the best it would do. There are almost no markings on the prop, measured with a ruler it appears to be only a 7" diameter, there is a 9 stamped on it - maybe a 9 pitch? The motor is pretty cold blooded but once it's warmed up runs well.

I was expecting more top end, was that unrealistic? Any guesses if a modern 25hp would do better? Based on the performance test numbers at Alumacraft I was hoping for closer to 20mph.

The boat is rated for 60hp, I'd guess the best option is probably to just go for a 60, but with the price of outboards if I can get 20mph out of a 25hp I'd call it good until I can upgrade to a bigger/newer boat.

[VMS]

If the motor is early 80's or older, chances are the motor is rated 25 hp at the engine...not at the prop. So..it would probably be acting more like a 20hp.

I'm guessing that boat is fairly heavy too. About the only thing I could think for you to try is change the trim angle pin up a notch or two to see if you can get the bow of the boat up higher. That may make it faster, although it may take longer to get the boat up on plane.

With a max hp of 60, you are way way WAY underpowered, so being under 20mph is not surprising. Pitch sounds about right for the motor too...

Steve

[marine_man]

I agree with VMS - I'm afraid that what you've got is all you're going to get with a 25 hp motor on a 18' boat...

marine_man

[Valv]

I agree too with a 25hp and a '82 18ft Lund you will not see much speed.

[JohnK]

I don't know the year of the motor, but from the looks it wouldn't surprise me if it was a mid to early 80's motor, so you're probably right it's more like a 20 hp - with 25 years of use on it too. So a new 25hp might perform better, but not a lot on the top end.

Trimming up the motor is a good idea. When I've had it out it looked like it was tucking under a bit, almost a negative trim if that makes any sense. If I can find out how to trim it up on this motor that could make a noticeable difference.

With a new motor I'd be looking for better usability and not just top speed, that's one big reason I'm even considering upgrading to a new 25. This motor takes a good 10-15 minutes to warm up enough not to stall when putting it in gear, and even then is extremely touchy and stalls far more often than not. I'll probably see about finding a good outboard/small engine repair shop to have them take a look this winter too.

[marine_man]

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If I can find out how to trim it up on this motor that could make a noticeable difference.

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The only trimming you'll be doing on this motor is with the trim pin, which goes between the lower engine mounting brackets. You'll have to manually move the pin up a hole at a time until you find perform the balancing act where you've got a hole shot you're happy with and a speed you're happy with because you won't get both at the same time.

Good luck!

marine_man

[chris63]

Crestliner not Lund,13.3?not bad for a 18ft and 25 horse,a 14ft with a 20 is lucky to see 20mph.Your not doing bad at all at 13.3for an 18 footer(heavy boat!)cyac63

[JohnK]

I took a look at the trim pin, 5 positions and it's right in the middle so there is room to adjust it. As you can guess it doesn't have much of a hole shot as it is and I'll sacrifice a bit there for a little more top end (such as it is).

This performance bulletin from Yamaha was why I was hoping to get close to 20mph:

http://www.yamaha-motor.com/assets/products/otb/bulletins/bulletin_2stroke_hpmidport_al_alm-fisherman160cs-25elr.pdf

It's good to hear that it's not really realistic for a 18' though - getting my expectations aligned with reality isn't a bad thing.

[ricqik]

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With a max hp of 60, you are way way WAY underpowered, so being under 20mph is not surprising. Pitch sounds about right for the motor too...

Steve

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I'm agree. When buying a boat always try to go with the max rating of the boat if possible. Otherwise it's like buying a superduty with a 5.4 and 3.36 gears. You're moving but not with heart.

[hanson]

You shouldn't have to move up too much in horsepower to achieve the results you want.

My early 80s aluminum 16' Mirrocraft with 60hp Johnson scoots it along at 30-31mph (Gps) with 2 good sized adults and fishing gear. My boat is rated for 85 hp which is kinda scary when I think about it.

[ricqik]

Last yr I road in my cuz's 16' crestliner w/40hp yammy and it can only muster 23gps. I guess I'm just used to mine. It's like going from a vette to a metro.

[Valv]

Quote:

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This performance bulletin from Yamaha was why I was hoping to get close to 20mph:

http://www.yamaha-motor.com/assets/products/otb/bulletins/bulletin_2stroke_hpmidport_al_alm-fisherman160cs-25elr.pdf

It's good to hear that it's not really realistic for a 18' though - getting my expectations aligned with reality isn't a bad thing.

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You are comparing a new 16ft with new 25hp with yours. You have a much heavier boat with less horsepower.

[Surface Tension]

If your going to keep the boat don't buy a new 25 for it.

Either sell the boat and buy a plain 16' or sell the outboard and get at least a 40 hp for it.

[swamptiger]

It depends a lot on the weight of the boat and the hull design, but most 18' boats would be underpowered with 25 hp. I have used a 30 hp 2 stroke Yamaha up in Canada on a 18' bare fishing boat that did a pretty good job. I have a Princecraft Starfish 15 with a 25 hp Evinrude 2 stroke that scoots pretty good with 2 guys and fishing gear. This boat only weighs about 300# and is rated for 40 hp. Performance drops off fast when you start adding weight to the boat with the 25 hp though.