hitting the rev limiter

[cathunter21]

im hitting the rev limiter on my motor about halfway between 3/4 throttle and WOT. its a 15 hp 4 stroke on a 1436. the prop was on it when i bought it and i looked at it today and it says 8P on it. so im guessing its an 8 pitch. i no i need to get a tach to see where im running on rpms but can anyone explain how to no what pitch to go to after i check my rpms? im completely clueless when it comes to stuff like this?

 

[Quackrstackr]

If you are hitting the rev limiter, you are probably quite a bit out of your recommended rpm range. They usually set those at several hundred rpm over the top end of the recommended.

You will lose approx. 200 rpm for every inch of pitch that you go up. Use that as a guideline to figure your pitch after you find out what the recommended operating range for your motor is.

Your prop isn't cavitating or anything, is it?

 

[CarlF]

Did you spin the hub on the prop???

 

[ben2go]

Sounds like the prop is getting air or slipping.How far below the bottom of the boat is the cavitation plate?Most manufactures recommend 1 to 1.5 inches below the hull.If you are hitting the rev limiter you are over revving the engine.

 

[cathunter21]

it is about 1.5 inches off the bottom of the boat. i never go any higher than 3/4 throttle because of over revving the motor. but my prop is still getting bite in the water.

 

[ben2go]

Have you pulled the prop and check the splines or key?I am not sure what locks the prop to the shaft on your motor.

 

[cathunter21]

no i havent what should i look for with this?

 

[ben2go]

Check to see if the prop and shaft still have their splines.Splines are like teeth that run around the shaft and inside the prop.A key just looks like a half moon shaped piece of steel.Make sure it isn't broken and the groves are square and true.Not rounded on the edges.The splines in a prop are designed to let go in case of a prop strike,same goes for the key type.

 

[cathunter21]

i just pulled my prop and the splines are completely perfect. after this is getting a tach and a new prop with the right pitch whats left?

 

[Quackrstackr]

You can put the motor in gear and make sure that your hub isn't slipping by turning by hand but that is probably not what it is from what you have described.

If your prop is not slipping and not cavitating, you need a bigger pitch.

 

[cathunter21]

does anyone know where i can get a tach to see my rpm range. and thanks for the help so far im clueless without you guys.

 

[wasilvers]

TinyTach seems like a nice little tach. I bought a faria for my boat and now wish I had bought this one.

https://www.tinytach.com/tinytach/index.php

Good Luck!

Will