Help new boat can't get to recommended WOT

[techlogic]

just bought a used 2007 monterey 194fs it was down in a town that was 4000ft above sea level brought it up to 7000ft and when i put it on the lake it would only get to 3200rpm WOT!! top speed was 35mph. it has the 5.0gxi (270HP) and the prop is a 14.3x21. is this strictly a prop issue or motor as well???

 

[vegasphotoman]

Re: Help new boat can't get to recommended WOT

I would think that a 2007 would be injected...so it SHOULD I would think have a sensor for barometric pressure........and would self adjust ...perhaps the local boat shop has proper test equipment to check your electronics and such

did you drive it at low altitude to a higher rpm before ya bought it?

and that prop to me sound fine...I had a 17ft with same prop....4400 rpms no prob with an older 3.0 120hp

never drove a new boat at altitude...7k isnt THAT high tho....just kinda high....gotta be another issue?

 

[techlogic]

Re: Help new boat can't get to recommended WOT

never had it out at low altitude but it has the 5.0gxi which is the injected model so it should just go. thinking either something up with fuel injection like didn't adjust for altitude or similar as i would mash the throttle down and the boat took forever to plain out and then it would only do about 30-32 top speed.

 

[H20Rat]

Re: Help new boat can't get to recommended WOT

even with fuel injection, you still lose a ton of power. A general rule of thumb is altitude in feet * .03 * hp at sea level / 1000. So in your case, you are down almost 60 hp at 7000 ft.

210 hp vs 270 hp is more than enough to justify a substantially different prop.

 

[Silvertip]

Re: Help new boat can't get to recommended WOT

Agreed on the altitude and power issue. EFI can compensate for the difference altitude makes on fuel mixture. It cannot compensate for the loss of HP.

 

[DuckHunterJon]

Re: Help new boat can't get to recommended WOT

Yup, there will be some power loss at altitude. Unfortunately, the only way you will know for sure will be to pull it out and run it at a lower altitude or take it to a mechanic familiar with fuel injection to run a diagnosis.

If it's purely altitude, you need to find a way to cram more of the less dense air in the intake ("But honey, the boat NEEDS this supercharger to run right at this altitude!").

 

[techlogic]

Re: Help new boat can't get to recommended WOT

ok, going to go with a 17 pitch prop 4 blade. it is on it's way as soon as I get it and go for test run will post results!!

 

[45Auto]

Re: Help new boat can't get to recommended WOT

Did you do a water test on it before you bought it? Compression test?

If so, how did it run at 4000'?

If not, hopefully you got a VERY good deal on it! Hard to believe a 270HP, 19' boat would see that much difference just because of the altitude unless something was wrong besides the prop.

Maybe it'll work out for you, good luck!

 

[QC]

Re: Help new boat can't get to recommended WOT

Check the tach!!! I never believe boats that will only reach 3200 RPM will also plane.

Oh, and I could see really marginal performance if the 4000' setup was already less than optimum.

 

[techlogic]

Re: Help new boat can't get to recommended WOT

ok, got new volvo penta 4 blade 17 pitch prop and took it out on the lake today.
definitely a difference in how the boat handles. got 45 mph tops and was able to get to about 4500 rpm so a major improvement. also get on plane a lot faster. so i am happy with prop but gonna try a 15 pitch to see if i can get rpm's up to the 5000 range and see.

will post results after try 15 pitch prop this weekend.