cant ajust trim...drive ratio....rpm of motor

[gregcb12]

i have a 88 chaparrel villian 111 24 ft closed bow 454 bravo 1 new 4 blade merc prop with a couple of dings in it now........my ?s.....when trying to put drive down or up it just makes a clicking sound....if i tap on the hydralic motor it will work but then stops again....also my boat will go 50 mph max at 4200 rpm....is the drive ratio wrong ? should it go faster? the motor is stock except for carb and manifold.....is 4200 rpm to much for that motor?i also have wet exhaust,keeping it in the salt will there be a proplem for the motor?i have zincs on the outdrive

 

[Don S]

Re: cant ajust trim...drive ratio....rpm of motor

If the motor runs when you tap on it, I would guess the motor has the brushes sticking probably due to corrosion. You can try dissassembly and cleaning, but it usually requires replacement when that happens.

Is 4200 your max rpm? Speed doesn't matter in a marine engine, it's the rpms that count. But you probably just need to adjust prop pitch to change rpm, not drive ratio.
The problem is, is finding out exactly which engine you have. Do you have a serial number?
The 330 hp 454's had a WOT rpm of 4200 to 4600 while the 88 365 hp engine had a WOT rpm of 4600 to 5000 rpm.
And going by the year of the boat is a waste of time, all it says is your engine and drive may be 87 or 88.

 

[gregcb12]

Re: cant ajust trim...drive ratio....rpm of motor

is 4200 a lot of rpm.......how long can i run at that rpm.....i can make the rpms higher (maybe 300 )by raising the trim but....i am afraid to rev it much higher.......and do you know if the inside of the engine is protected when i leave it in its slip........i have zincs on the outdrive i dont know about the motor......thanks so much for your help...this is my first boat and my first yeat in the salt water ......i will figure out which engine i have for my next ?s

 

[Don S]

Re: cant ajust trim...drive ratio....rpm of motor

is 4200 a lot of rpm.......how long can i run at that rpm.....i can make the rpms higher (maybe 300 )by raising the trim but....i am afraid to rev it much higher.......

You're asking a wierd question here. If you raise the drive high enough, you should be able to get 10.000 rpm and blow the engine.
The trick is to trim up till you get the highest rpm AND the highest speed at the same time. Then you have optimum trim (It changes constantly, so don't think it will always be the same position)
Trim up and watch your rpm and speed while at WOT., When the rpm goes up and the speed goes down, you are trimmed to high. You want to find the sweet spot where the rpms are max and the speed is max.
Then, you will know what your WOT rpm is.

 

[gregcb12]

Re: cant ajust trim...drive ratio....rpm of motor

ok well 4300 is when it is going its fastast and the trim feels like it is in the sweet spot..........how long can you run the motor like that with out hurting it?or is that a safe rpm? and how much is that part i need for the trim is it a pump or a motor or both? thanks again......and what about the salt water being inside the engine all the time?

 

[gregcb12]

Re: cant ajust trim...drive ratio....rpm of motor

what is wot?

 

[Don S]

Re: cant ajust trim...drive ratio....rpm of motor

Wide Open Throttle, sorry about that :%

 

[Don S]

Re: cant ajust trim...drive ratio....rpm of motor

ok well 4300 is when it is going its fastast and the trim feels like it is in the sweet spot..........how long can you run the motor like that with out hurting it?

Then 4300 is likely to be your WOT (Wide Open Throttle) rpm and you adjust your prop from there depending on exactly what engine you have.

how long can you run the motor like that with out hurting it?

You can always run at that rpm, all day if you want, but in the long run, your engine will not last very long. Just like in NASCAR. They build the best engines, and the higher the rpm, the shorter the engine life.

I'll have to look up prices and availability of the trim pump parts.

 

[gregcb12]

Re: cant ajust trim...drive ratio....rpm of motor

thanks this is a great site........how do you get a picture of your boat on your posts or replys

 

[QC]

Re: cant ajust trim...drive ratio....rpm of motor

Welcome to iboats gregcb12!! Here's some info on posting a picture:

How to post a picture

Also, since you are trying to figure out how to run her etc. If those prop dings are pretty small, clean them up with a file or you can even use vice grips to straighten tiny little wiggles out. Then try the top speed thing again. If the dings are half the size of a dime or bigger, it is probably time to have somebody work on it.

If you can't get the boat to "porpoise" (rhythmic bouncing of the bow up and down) at your highest trim setting, then I would try shifting some weight aft. You may get more speed and RPM at the point just before she starts to porpoise, but if she won't porpoise at all there may too much weight forward to get all the speed she has. As Don is telling you, we need to determine if the prop is correct by noting the max RPM at WOT, trimmed for the fastest you can go AND with a typical load in the boat. Ya know, fuel, beer, people, more beer, maybe some food, toys etc. Definitely get rid of any excess weight you can, but she needs to be propped for how you will use her most of the time. Based on your top speed that you reported, I think it is pretty close, but the fact is she may be more responsive and possibly faster with less propeller pitch and some more RPM, I wouldn't do anything until you're sure that your getting all you've got though. This is the part where you might get to spend more $ . . .