1989 omc 4.3 no top end power

[newfie12]

I have just purchased this boat. I idles perfectly and runs perfectly until i reach about ten km/hr.
then it seems to bog out and sputter. I did notice a "mist or haze" coming out of the carb.

here is a list of what i have done with the boat:

2 new cylinder heads and valves
all new upper gaskets
new thermostat
new coil
replaced points and condenser with electronic

does anyone have any ideas?

 

[Howard Sterndrive]

Re: 1989 omc 4.3 no top end power

sounds like the carb is running out of fuel - suspect fuel filter, fuel pump, lines from tank including anti-siphon valve
that backfire of sorts is what outboard guys call a "lean sneeze" - it's what an engine does when the mixture gets super lean (all air - almost no fuel)

 

[newfie12]

Re: 1989 omc 4.3 no top end power

ok i will run a compression test today, and replace the fuel filter and check the fuel pressure, any idea on what the fuel pressure should be for this boat?

 

[newfie12]

Re: 1989 omc 4.3 no top end power

and would it be possible the the carb is not set up correctly, if so should adjustments be made on the front screw on the carb?

 

[Howard Sterndrive]

Re: 1989 omc 4.3 no top end power

and would it be possible the the carb is not set up correctly, if so should adjustments be made on the front screw on the carb?

you say it idles well, so do not touch the idle mixture screws - that would not be your problem

 

[newfie12]

Re: 1989 omc 4.3 no top end power

Ok, thanks so much for the help. I will run through those ideas that you gave me and post the results when i know.

Thanks again

 

[newfie12]

Re: 1989 omc 4.3 no top end power

ok so i ran a compression test numbers are roughly 125 across the board, checked all the fuel lines and the valve, everything checks out well. the fuel filter was new but i popped another one on just to be sure. i did find one pink wire coming from the fuel tank that was chaffed about half way through. Is it possible that was my problem?

 

[Boats-A-lots]

Re: 1989 omc 4.3 no top end power

This happened to me last fall while crabbing. In a slow no wake zone, ran fine, as soon as I got to open water and punched it, it would bog down and almost not run at all. I set my crab traps, and putted around the bay, after about a half hour is started running like it should. When I got the boat back home I checked the gas in the tank and it was brown. I drained it, (with a small fish tank hose up the drain plug into the gas vent line) changed the spark plugs (I went one step up to a hotter plug) and put new gas in it. The next time I took it out it ran perfect.

 

[john cole]

Re: 1989 omc 4.3 no top end power

what does it do in neutral? does it get to wot ok, make sure you have your timing set for wot throttle not idle, i found this out the hard way, the guys on here helped me out a bunch. If your gas is clean and getting enough then time to look at ignition issues.

 

[newfie12]

Re: 1989 omc 4.3 no top end power

what does it do in neutral? does it get to wot ok, make sure you have your timing set for wot throttle not idle, i found this out the hard way, the guys on here helped me out a bunch. If your gas is clean and getting enough then time to look at ignition issues.

I think you may be onto something here. WOT in neutral seems fine. I just tried turning the distributor while on the water, could you tell me the proper procedure for this?

 

[bruceb58]

Re: 1989 omc 4.3 no top end power

I think you may be onto something here. WOT in neutral seems fine. I just tried turning the distributor while on the water, could you tell me the proper procedure for this?

You need a timing light. There are a lot of videos online that show you how to use one.

By the way WOT at neutral means absolutely nothing. You could have half of your spark plug wires off and it would rev fine in neutral.

Definitely check and double check that you have your spark plug wires on in the correct firing order. Amazing how well it will idle with 2 of them crossed.

 

[john cole]

Re: 1989 omc 4.3 no top end power

Correct that it will go to WOT with out all plugs firing but you will pick up a vibration and if the timing is off it again will develop a vibration that won't usually be there at idle of low RPM's. you should have a light with the advance feature on it, makes it soooo much easier to set the timing. and re check your plug wires to be sure they are good. i just had 1 go bad on my 4.3L and it caused me to lose all my power, and it was new. one easy way to do that is to take turns hooking you timing light to the different wires by the plugs and see if it getting spark there. just a couple of thoughts from my experiences.

 

[Silvertip]

Re: 1989 omc 4.3 no top end power

ok so i ran a compression test numbers are roughly 125 across the board, checked all the fuel lines and the valve, everything checks out well. the fuel filter was new but i popped another one on just to be sure. i did find one pink wire coming from the fuel tank that was chaffed about half way through. Is it possible that was my problem?

The pink wire is the sending wire that goes to the "S" terminal on the fuel gauge. It is definitely NOT the problem.

 

[Silvertip]

Re: 1989 omc 4.3 no top end power

If you used a feeler gauge to check the point gap you may have not done that correctly. A dwell meter is a far more accurate way to do that. After dwell is set you then set the timing using a timing light. You cannot get within 5 degrees of correct ignition timing by ear and risk destruction of a perfectly good engine by trying. A common recommendation here is that if you intend to do any work on the boat yourself, buy a service manual for your specific engine/drive. It saves frustration, time, money, and prevents costly mistakes (if you use the manual of course).

 

[newfie12]

Re: 1989 omc 4.3 no top end power

If you used a feeler gauge to check the point gap you may have not done that correctly. A dwell meter is a far more accurate way to do that. After dwell is set you then set the timing using a timing light. You cannot get within 5 degrees of correct ignition timing by ear and risk destruction of a perfectly good engine by trying. A common recommendation here is that if you intend to do any work on the boat yourself, buy a service manual for your specific engine/drive. It saves frustration, time, money, and prevents costly mistakes (if you use the manual of course).

I am going to get a timing light today and try that, hopefully that solves the problem, i am taking it on the water tomorrow. i did swap out the points and condenser with electronic since my last trip out. Also i did manage to get an omc service manual on disk.

bruceb58 I have checked the firing order two or three times now but i will check it again, just to be sure. I am guessing that the firing order stamped on the intake is correct.

I feel like i am overlooking something small as well, so i am going to go back through and recheck everything that evreyone has suggested. I will keep the progress posted.

Also does anyone have any idea what kind of speed or power this boat should have when working correctly, it is a 1989 18ft cadorette bowrider the only thing marked on the sterndrive is cobra.

 

[newfie12]

Re: 1989 omc 4.3 no top end power

So i managed to get back at the boat yesterday, turns out it was bad gas, drained all the gas out and put new in and its running perfect.
Thanks everyone for the help, hopefully i can return the favor someday.