cavitation problem on pontoon PLEASE HELP!!!!

[tommytoon]

i have a 21' crest pontoon with a 1986 75 hp. mercury motor,the cavitation plate rides about a inch below the water when boat is not moving just


sitting in the water. i have a 3 blade prop with 2832-13 stamped on it. at wot the boat is going along at 4100 rpm and then it revs and the boat

slows until i back it off, at the cavitation or rev point the tac is about 5000 rpm. it does this going straight down the lake. any suggestions or

comments would be helpful and thank you in advance!!

 

[SparkieBoat]

Re: cavitation problem on pontoon PLEASE HELP!!!!

is it power tilt and trim?? you need to make sure the rod that stops the motor from trimming all the way down is in the last hole or remove it all together, trim motor all the way down., you could also try lowering your motor..sometimes 4 blade props will not cavitate as bad as 3 blade props.

 

[tommytoon]

Re: cavitation problem on pontoon PLEASE HELP!!!!

Power trim only run it all the way down though i have tried to adjust trim with no success thanks for your input sparkie

 

[steelespike]

Re: cavitation problem on pontoon PLEASE HELP!!!!

About an inch below water at rest seems really high to me.Have to wonder if it is a short shaft motor or mounted way too high.

 

[SparkieBoat]

Re: cavitation problem on pontoon PLEASE HELP!!!!

yep...what size shaft motor was on the boat before????

 

[tommytoon]

Re: cavitation problem on pontoon PLEASE HELP!!!!

it is a long shaft for sure and it is the motor that came with the boat when i bought it used. the motor is in the lowest holes as far as adjustment so im LOST!!!! has anyone ever heard of a kit to lower the transom mount sold by manufactuer or homemade spacers to lower that into the water or is that impossible . the steering would hit the transom if i drilled holes to lower the motor more

LOST AND CONFUSED!!! THANK YOU GUYS FOR ANY HELP IN ADVANCE

 

[steelespike]

Re: cavitation problem on pontoon PLEASE HELP!!!!

Is 4100 the normal max rpm or the point where it loses grip? Can you get us the speed at 4100? rpm doesn't tell much without the speed.

 

[tommytoon]

Re: cavitation problem on pontoon PLEASE HELP!!!!

i called mercury yesterday and they said that motor should be at 5000 to 5500 rpm at wot. it only goes 4100 rpm at wot could that make any difference? i only get the 4100 out of it and its fine and then every time out it will start to ventilate or cavitate. problem with the motor?????

 

[SparkieBoat]

Re: cavitation problem on pontoon PLEASE HELP!!!!

you MUST figure out why it is cavitating, You could try posting some pics of the motor/back of toon. other than that you may have to pay a professional to figure it out for you. I just cannot think of what could be your problem from the info you have provided. it is a bit confusing. I am suspect you may have a 20" shaft motor even though you said you are sure it is a long shaft. but a picture is worth a thousand words. yes you should get 5500 rpm