recomend prop size?

[hoverman]

sunday took the family to mission bay for some tubing....my boat is a 1991 monterey scr 206 with a mercruise 5.7 alpha one turning a 3 blade 14x19 aluminum prop with a 1.5 gear ratio....First gas mileage sucks big time!! second with 3 people on board and pulling one on a tube the boat doesnt seem to plane very fast even at full throttle and secondly i can not get close to the 4400 rpm wot the best i seem to get is 3500 rpm...what do some of you suggest? hydrofoil? prop change? im guessing on the prop size too the only numbers on the prop are 1916 19 and thats it when measured with a ruller i get 14 in diameter......

 

[TilliamWe]

Re: recomend prop size?

Confirm your tachometer's accuracy first.
Then confirm that the carburetor's secondary plates are opening all the way.
Then confirm that the drive is going all the way down.
Then confirm that your boat doesn't have a bunch of water in the hull.
Confirm that the exhaust shutters are not melted off and stuck un the exhaust.

Only after all those things check out, then try experimenting with props. But a 19p sounds just about right to me. So I am surprised that the boat can't turn it. I think you have an engine issue.

 

[hoverman]

Re: recomend prop size?

well the hull is not full of water i know that...drive is all the way down and tilt and tril work just fine...i will have to get back to you on the secondarys and the tach...how ever my gps read a top speed of 37 mph...i hear no clattering from the exhaust indicating they have melted the rubber off...

 

[TilliamWe]

Re: recomend prop size?

i hear no clattering from the exhaust indicating they have melted the rubber off...

When they melt enough to fall off the post that holds them, they don't rattle, they are stuck in the bottom of the Y-Pipe. Plus the new style ones don't clatter like the old ones anyway, cause they are shaped different and work differently.

 

[steelespike]

Re: recomend prop size?

Cinfirm it is running on all cylinders.You wouldn't be the first to not realize
a boat was on 7 cylinders.Also do a compression check.

 

[SEAMIKE]

Re: recomend prop size?

I had a similar problem last week on my Larson 220 Cabrio, fitted with a 5.0L, carb, alpha 1, and a 3 blade prop,could only get 28mph, with a WOT of 4200 rpm, boat listed heavily to port, and struggled to get to 28 mph, tried to trim the drive out as far as I could, without the prop ventilating,only thing that had changed was the original prop was a 4 blade which was damaged, which Larson changed for the recommended 3 blade,gave it back to Larsons for them to investigate, and found that the choke was the culprit, took it back out on the weekend, got 40mph, at 4600 rpm, boat behaved perfectly.

 

[hwsiii]

Re: recomend prop size?

Hover, if you are trimming the outdrive up correctly at WOT you should be doing almost 50 MPH. In my opinion you definitely have a motor problem.


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