boat will not go over 3500 rpms

[dabruza26]

i have a 1986 regal with 4.3 2bbl rochester carb on it. i have had the car rebuilt 2 times by a good carb guy. and still the best i can do is 3500 rpm. when i am wide open on throttle there is popping coming out the top of caarb like every 35 secs or so if i back it down just barely it stops doing that. i think i should be able to get at least 4800 rpms out of this boat maybe i am wrong. i would really like to think that a 19.5 foot boat with that size motor in it would go much fast then 39 mph . i have been to local prop store and told them the same story bought new prop and gain like 2 mph. i am at a loss just seems like not at its peek performance to me anyone that can help would be great going to lake in one week could use the extra power.

 

[91rr]

Re: boat will not go over 3500 rpms

Here are some steps you can take to check. I kind of had the same problem only to realize my engine is just worn out. What can you expect out of a 25 year old engine? My was the same year only a 5.0L. Good luck.

http://forums.iboats.com/showthread.php?t=295070

 

[dabruza26]

Re: boat will not go over 3500 rpms

yeah i know i forgot to mention this motor is brand new as of july last year

 

[91rr]

Re: boat will not go over 3500 rpms

What size prop are you running? What was your rpm's before you switched it and what size did you go up to?

 

[JSMoore]

Re: boat will not go over 3500 rpms

I don't pretend to be an expert on that. But, if you are getting a pop back through the carb at full throttle, it sounds like one of, or a combination of the following:

1. Timing set wrong. (Should be 6*BTDC for 89 Octane or 1* BTDC for 86/87 Octane)
2. Point gap/dwell set wrong. (Should be 0.019" or 37-41* dwell)
3. Mechanical advance in the distributor not working right. (Springs get weak & parts get stuck or worn)
4. Some other part of your ignition system breaking down under the "stress" of WOT.

There are probably a few other things that might cause that. But, I'd look for the simple stuff first.

Just so you don't expect too much of the 4.3L V6 you have, the book on it calls for a max WOT RPM of 4200 - 4600. You're not too far away from that now. If you can figure out what's causing that popping back through the carb at WOT, you will probably have found why you're not coming closer to book RPM.

Hope this helps some.
JSMoore

 

[GELRunner]

Re: boat will not go over 3500 rpms

Dabruzza - Funny you should post this, I had the exact problem with my 1982 Cobalt today! Check your plug wires, and ensure you have the firing order correct!

 

[dabruza26]

Re: boat will not go over 3500 rpms

well thanks every one for the help but got the turd out on the water today and it now wont go over 2200 rpms and flooded it self so bad i had to remove all the plugs. and crank the engine to blow out all the gas and bpinch of the full line. backk plugs on both sides were soaked with gas and the front 4 were not and all black big time. and after still would not go over 2200 rpms so i am thinking it is prob carb related. which is really dumb because i know noghting about this stupid carb already been rebuilt 2 times and i am out of answers so i guess back to the shop it goes. any one wanna buy a boat out of st louis lol

 

[JSMoore]

Re: boat will not go over 3500 rpms

Frustrating! I know....

Rather than mess with kits and me, (or somebody else), that doesn't know what they're doing inside a carb, I decided to go the "Re-manufactured" route. I ordered a complete, re-man carb for my OMC Cobra, 4.3, 2BBL, from Flying Fish Carburetors. I can't rave enough about the product they sent me. They pre-set each carb they send out to YOUR specific boating application. When I put this thing on, I swear, the only thing I had to do was increase the idle speed about 50 RPM. Everything else was "Plug 'n Play"! Great warranty! Great folks to deal with. (No.... I don't work for them.)

So, rather than throwing money at something that's not worked for you twice now, you may want to give a thought to the "re-man" route.

Just a thought.
JSMoore