Repowering Above Recommended Horsepower

[fishrite]

I have a 97 Pro-Line 170 Sportsman with a 90 HP Johnson SPL. At sea level, the boat is a 30-35 mph boat. Not too bad for your average fishing boat.

Here is the problem. I live in CO. I love this boat, but at 5-9,000 ft MSL I am lucky to see 25 mph and have great difficulty getting up on plane. I have switched out props, but at the end of the day, altitude consumes horsepower.

Pro-Line outfits this boat with 90-115 hp outboards. So my questions are:

1) Should I repower this boat at all? I do like it, but it is a slug right now.

2) If I do repower, should I go above the recommended 115 HP range to compensate for the loss of horsepower at altitude? As long as the weight differential is minimal, are there any real issues here?

Just trying to make the boat a bit more enjoyable.

Your thoughts are appreciated.

Ty

 

[Dakota47]

Re: Repowering Above Recommended Horsepower

A Yamaha 115hp 2 stroke would be great for that boat..

 

[tashasdaddy]

Re: Repowering Above Recommended Horsepower

you have ground level fuel jets in the carb. get the jets you need for the high altitude. should save you a lot of money, but if you are planning a trip to sea level, save you sea level jets.

 

[Don S]

Re: Repowering Above Recommended Horsepower

What ever engine, or size, 2 or 4 stroke. Get EFI. They handle the altitude much better. Along with a high altitude gear set in the lower.

 

[fishrite]

Re: Repowering Above Recommended Horsepower

you have ground level fuel jets in the carb. get the jets you need for the high altitude. should save you a lot of money, but if you are planning a trip to sea level, save you sea level jets.

The boat shop recommended against re-jetting; said it couold run too lean and then we have other issues. It is definitely running rich. They told me to go down one pitch size. Well, I went from a 19 pitch to a 15 pitch and that barely works. They are now out of business...

Since I consistently fish well over 6000 feet, it seems re-jettting may be worthwhile before repowering, if I can find a source for the jets. Will post in the Johnson engine forum next.

Thanks

 

[Caveman Charlie]

Re: Repowering Above Recommended Horsepower

The boat shop recommended against re-jetting; said it couold run too lean and then we have other issues. It is definitely running rich. They told me to go down one pitch size. Well, I went from a 19 pitch to a 15 pitch and that barely works. They are now out of business...

Since I consistently fish well over 6000 feet, it seems re-jettting may be worthwhile before repowering, if I can find a source for the jets. Will post in the Johnson engine forum next.

Thanks

Maybe there is a reason there out of business.

 

[Texasmark]

Re: Repowering Above Recommended Horsepower

Don't forget to run it by your insurance agent before you do. Hopefully, there is some sort of altitude formula that can be applied to allow a certain level of "apparent" overpowering due to the altitude.

Would be in your best interest to check it out.

Mark