boat will not plane out and rpm will not go over 1000 rpm in gear

[markone]

i`m new to this forum and hope someone can help i have a 1987 wellcraft 192 classic with a 140hp 3.0,when i`m in gear it doesn`t seem to rev past 1000 rpm,my top speed is 10 knots and it won`t plane out,but whilei`m in neutral it revs as high as i want it to, it also makes a rattle noise in gear when reving past 800 rpm,i`m thinking i have the wrong prop but not sure the prop on it now is a 15 1/2x21 any help would be appreciated thanx in advance

 

[dozerII]

:welcome:At the top of the Mercruiser forum there is a Sticky called For Adults only, open it and check out # 15 it will get you started on finding the problem.

 

[markone]

boat will not plane out and will not rev past 1000 rpm in gear

hi i`m new to this forum and hope someone can help me i have an 87 wellcraft 192 classic with a 140hp 3.0 it will not rev past 1000 rpm in gear it will not plane out and the motor rattles like rocker arms are out of adjustment at about 800 rpms,but when in neutral will rev as high as i want it to gowith no noises. i`m thinking it may have the wrong prop it has a 151/2x21 prop now .i`m also running a prealpha drive from a 2.5 any help would be appreciated thanx in advance

 

[markone]

sorry if i sound dumb but as i said i`m new to this forum, what is a sticky,and i can`t seem to find for adults only

 

[DeepBlue2010]

A sticky is a thread (post) that is not allowed to age and lose its position on top of all posts as people continue to post over it. It remains on top of the list all the times. On the main page of this forum, the very first post is titled "Adults Only" by Don S (God rest his soul)

# 15 in the list inside this post is what Dozerll was referring you to. Here is a direct link to it

http://forums.iboats.com/forum/engin...-no-exceptions

 

[markone]

thanx deepblue2010

 

[markone]

ok i looked at the sticky but there is nothing there i see that will help me with my problem, i do know about boats altough i am a novice boater,i`m just curiuos if i`m on the right track by thinking my prop is wrong {anybody?}

 

[ziggy]

this link is for can't reach wot spec.
your prop could be too much and it is one of the possibilities in the link. myself. i'd start with a compression test to see if ya got something to work with and go from there. also. the factory mercruiser service manual may have a troubleshooting guide in it that can be helpfull.
go through the won't reach wot list one by one and be sure each is correct for your engine drive set up.

fwiw, reving it up in neutral, no load, means nothing as to engine health. also, don't rev it to high w/no load. it isn't great for your engine.

 

[Bondo]

hi i`m new to this forum and hope someone can help me i have an 87 wellcraft 192 classic with a 140hp 3.0 it will not rev past 1000 rpm in gear it will not plane out and the motor rattles like rocker arms are out of adjustment at about 800 rpms,but when in neutral will rev as high as i want it to gowith no noises. i`m thinking it may have the wrong prop it has a 151/2x21 prop now .i`m also running a prealpha drive from a 2.5 any help would be appreciated thanx in advance

Ayuh,..... The hi-lighted statement tells me, ya got a fuel restriction,...

Have ya changed the fuel Filters,..??

If it's runnin' Lean, that rattlin' is Detonation, eatin' up the internals of yer motor,... Don't do it anymore,....
It'll hole a piston in No time,....

Have ya done a Tune up on it,..??
How 'bout a Compression test,..??

 

[markone]

i put a used motor in had the carb rebuilt ,brand new fuel pump,brand new fuel filters in line in the carb and in the pump,new plugs,new wires,new,points,new,coil,new cap and rotor,i`m using above floor gas cans because my in floor tank got crud in it and i had to rebuild the carb again,i don`t let it make the noise because i know it`s not good i just baby it .i have to check compresson and get back to.but every thing is new that`s why i thought maybe a prop problem

 

[thumpar]

Was the drive ever changed? It could be the wrong ratio. The prop might be wrong but you are not going to gain the other 3500 RPM or so you should be getting just from a prop change.

 

[markone]

well the link that ziggy gave me gave some good options to look in to. this boat i assembled from 3 different boats all similar boats, and i used an outdrive that i knew worked but now that i think of it i`m not sure what the gear ratio is in that outdrive i have 2 others that i know are for a 2.5 liter i should try 1 of those and see if it is a gear ratio problem.

 

[markone]

so my compression is 120 per cylinder,no problem there, but like bondo tells me starving for fuel seems like my problem,what should i do to rectify my fuel starvation?

 

[Watermann]

You're going to have to go over the fuel system again, seems like the creeping fuel crud you fought is still in the game.

 

[Bondo]

well the link that ziggy gave me gave some good options to look in to. this boat i assembled from 3 different boats all similar boats, and i used an outdrive that i knew worked but now that i think of it i`m not sure what the gear ratio is in that outdrive i have 2 others that i know are for a 2.5 liter i should try 1 of those and see if it is a gear ratio problem.

Ayuh,..... That sounds logical,.....

 

[DaveG55]

Im having trouble believing that gear ratio could be far enough off to limit WOT to 1000. Especially if the current drive is from a similarly sized boat.

 

[thumpar]

Im having trouble believing that gear ratio could be far enough off to limit WOT to 1000. Especially if the current drive is from a similarly sized boat.

It can happen.

 

[Watermann]

Not sure MC manufactured an outdrive with a gear ratio that would make any of their boat motors only turn 1000 RPMs and knock over 800. Unless you have a monster paddle wheel on the back.

 

[DaveG55]

It can happen.

I suspose, but it would seem to me to have to be a perfect storm type situation.

When I changed ratios, by one step, RPMs changed like 300 rpm. It was enough that 2 inches of pitch to correct. Now even if the ratio changed 4 steps and it was over propped I have trouble seeing it loose 3500 rpm. It's my understanding, and I've been told on here, that any ratio can be used behind any engine as long as it's propped to the correct wot range.
If im not seeing this correctly please help me understand.
Perhaps the op could post up his drive ratio and his prop and run it through one of the prop calculators.
Otherwise, if I were the op I'd be looking somewhere else, like fuel.

 

[thumpar]

Not sure MC manufactured an outdrive with a gear ratio that would make any of their boat motors only turn 1000 RPMs and knock over 800. Unless you have a monster paddle wheel on the back.

Put a 1.32 behind a 120hp.