OMC 4.3 wont go faster than 20mph

l. miller · Jul 5, 2009

1986 seaswirl ran great last year...this year would not start? changed the points and condensor fired right up and purred. took it to the lake fired right up but would only go 20 max? gapped points three times to 19 like the book says where should I look next how does the spark advance work ? my omc repair manual does not go into this topic. any suggestions would be greatly appreciated....4.3 v6 2-barel carb. the book says I should have a prestolite distributor I am assuming this is correct. thanks again

mkast · Jul 5, 2009

Re: OMC 4.3 wont go faster than 20mph

20 mph at what RPM?

Bondo · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

gapped points three times to 19

Ayuh,... Points are Set with a Dwell Meter.....

MikDee · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

That is a conventional marine distributor. Take off the distributor cap, and grab the rotor, you should be able to turn it clockwise some, and it should spring back on it's own, if not the advance mechaism under the breaker plate is not working properly, take off the breaker plate, and fix it, usually it just needs to be free'd up, cleaned, & lubed.

l. miller · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

thanks for all of your quick responses, I wish I had a dwell meter or even knew somebody with one, yes I would like to set the points correctly but I can only work with what I have for now. thanks for your advise Bond-o. and unfortunatly mkast I really did not pay attention to rpm's when I was on the water yes I am a rookie but learning and wont forget next time, and MikDee thank you very much for your response checked advance and yes it worked fine, wot should be 4200-4600 and I am only reaching 2400 with no load,changed both water seperator and fuel filter, did not help. I know theres alot of other things to check so I will get started with a complete tune up...thanks again for your time and advise guys.

Bondo · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

did not help. I know theres alot of other things to check so I will get started with a complete tune up...

Ayuh,... There's a "Can't reach WOT" posting in the Adults Only section at the top of this forum...

Good Luck...

scipper77 · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

l. miller said:
I am only reaching 2400 with no load

Just want to be sure you know not to rev the engine if it's on ear muffs. If you are revving in neutral in the water you should be ok.

MikDee · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

Another item to check, I don't know if this apply's, but check your firing order closely, there could be 2 wires crossed, and you'd never know it, except for a sudden loss of power, because I've seen it happen.

1,3,5 front to back on the right side of the engine as you face it, 2,4,6, on the left side, distributor turns clockwise, firing order is 1-5-3-6-2-4, it should be embossed on the top of the intake manifold.

l. miller · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

MikDee very happy to see that your still here thats extremely kind of you, about the firing order looks ok per my manual says for 4.3L omc cobra 1-6-5-4-3-2,

Bt Doctur · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

1,6,5,4,3,2 is correct

l. miller · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

sorry wasn't finished, and 1,3,5 2,4,6 like you said why the difference I don,t know but any how looks as if I have learned another important step as far as running the motor with ear muffs, I thought it was ok as long as I didnt engage the prop thanks for your advice scipper77. today the guy at precision marine told me to clean the spark advance spring and weights and lube them to make sure they are moving properly because he had the same problem before. looked and moved ok but actually wasn't advancing enough, I did this but did not change at all still drops out exactly at the same rpm 2300-2400 dont know where to go now dont want to rev anymore with the ear mufffs running. the guy at the marine shop actually talked me out of buying new set of spark wires and plugs if motor is running good at low rpm should not be the problem he said. and yes it fires right up and runs very smooth up to 2000 rpm. thanks again for giving me your time and advice,

MikDee · Jul 6, 2009

Re: OMC 4.3 wont go faster than 20mph

l. miller said:
MikDee very happy to see that your still here thats extremely kind of you, about the firing order looks ok per my manual says for 4.3L omc cobra 1-6-5-4-3-2,

Oops! Very sorry for posting that wrong firing order!

Guess I forgot to engage brain, before fingers :redface: But, I knew it sounded familiar, 1-5-3-6-2-4 happens to be the right firing order for a Chevy straight 250-6cyl!

I guess it's my "old skool" train of thought kicking in Here's a handy link:
http://www.aa1car.com/library/chevy_firing_orders.htm

l. miller · Jun 21, 2010

Re: OMC 4.3 wont go faster than 20mph

Its been awhile since I have got around to following up on speed problem,a long while...but here goes, when we replaced the points in the distributor that season, we ended up putting the spring on the points set backwards. go figure, $350.00 later at the boat shop it runs fine again. that was a very expensive little mistake. I have alot to learn and learning everyday thanks all.

180shabah · Jun 21, 2010

Re: OMC 4.3 wont go faster than 20mph

...bet you won't do it again

OMC 4.3 wont go faster than 20mph

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