52mph WOT! What gives 25' Others get 70+
#12
Sounds like you need a 3 blade prop - BUT the prop is not the problem.
You are not producing the HP you think you are.
With 500 HP you should easily turn that prop to over 5000 RPM.
Either you have the wrong cam for a boat engine or something is really wrong inside the engine.
With 500 HP you should be running at least a 25 mirage + to 5100 RPM.
You are not producing the HP you think you are.
With 500 HP you should easily turn that prop to over 5000 RPM.
Either you have the wrong cam for a boat engine or something is really wrong inside the engine.
With 500 HP you should be running at least a 25 mirage + to 5100 RPM.
#13
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Get us the motor specs on the motor. There are a lot on here that will be able to tell if the specs add up to a good boat motor.
My guess is wrong cam selection.
#15
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good thinking it might be 515 with car headers but not with crap boat manifolds that are just an open chamber. my guess is that its basically a stock 454 with a cam/ intake manifold
#17
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Was it dynod? (pretty sure I know the answer to this)
Who tuned it?
If you cross connected the spark plug wires you wont be able to pull any RPM.
The guys so far are all correct-car engines typically get great exhausts and run way more duration and valve overlap than a boat engine will.
Uncle Dave
#18
A standard merc ingnition rev limter is 4350 , put in a msd dist and ingntion and see what happens
if you have the hp you say you are on the limiter and thats why you are stuck at 4400 and you should then go with a bigger prop after you fix rpm problem . seen this problem before on a friends build , gave him my extra crane box ( fire wire merc ) and it took care of the problem , You can but a dist from msd wiith a rev limiter in it have fun
if you have the hp you say you are on the limiter and thats why you are stuck at 4400 and you should then go with a bigger prop after you fix rpm problem . seen this problem before on a friends build , gave him my extra crane box ( fire wire merc ) and it took care of the problem , You can but a dist from msd wiith a rev limiter in it have fun
#19
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Did the boat pull more than 4400rpm before the new motor? If so then rev-limiter is not the problem.
If that's not the problem that much HP should pull a 23-24 Bravo past 5000rpm. If you have stock exhaust than the HP number is down under 500 more likely 450-475 in the boat.
My mild 468 on the dyno pulled 407hp but is probably around 365hp in the boat since I still got stock exhaust. My boat is 24ft and I can pull a 22 Bravo to 4900rpm and a 26 Bravo to 4300rpm. I'm still looking for a 24 Bravo to try out.
If that's not the problem that much HP should pull a 23-24 Bravo past 5000rpm. If you have stock exhaust than the HP number is down under 500 more likely 450-475 in the boat.
My mild 468 on the dyno pulled 407hp but is probably around 365hp in the boat since I still got stock exhaust. My boat is 24ft and I can pull a 22 Bravo to 4900rpm and a 26 Bravo to 4300rpm. I'm still looking for a 24 Bravo to try out.
#20
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A standard merc ingnition rev limter is 4350 , put in a msd dist and ingntion and see what happens
if you have the hp you say you are on the limiter and thats why you are stuck at 4400 and you should then go with a bigger prop after you fix rpm problem . seen this problem before on a friends build , gave him my extra crane box ( fire wire merc ) and it took care of the problem , You can but a dist from msd wiith a rev limiter in it have fun
if you have the hp you say you are on the limiter and thats why you are stuck at 4400 and you should then go with a bigger prop after you fix rpm problem . seen this problem before on a friends build , gave him my extra crane box ( fire wire merc ) and it took care of the problem , You can but a dist from msd wiith a rev limiter in it have fun