Omc 3.0 not getting into high rmps in gear in water

Hello. I have recently developed a problem with my 1986 OMC 3.0 engine. Engine works fine while testing in the driveway, even when I put it in gear it still gets to the high RPMS but when I put the boat in the water the engine will not get into high RPMS when I put it in gear. The engine still goes into high RMPS when I manually push the cable forward or when just push on the carburetor arm. I have changed the points and adjusted the timing and nothing. Then I installed electronic ignition and still the same problem. The only thing I can think of is that I did change the transom seal before the problem started. Could I mess something up while doing it? I did not take anything apart just pulled the new seal over the outdrive and installed it. I did the same thing a couple of years ago and did not have this problem them. Please advise. Any insight would be very appreciated.

Re: Omc 3.0 not getting into high rmps in gear in water

change the fuel filter

Re: Omc 3.0 not getting into high rmps in gear in water

Thank you. I've ordered one. I hope that this will take care of it.

Re: Omc 3.0 not getting into high rmps in gear in water

Does anybody think that I should replace the fuel line as well? Currently I have a copper line in my boat. I am not sure if a copper line is a good option. That's how I bought it and it ran OK for 2 years. If I should replace what size of the new hose should I buy? Is there an anti-siphon valve on these old boats? Where is it located, by the fuel pump or the tank somewhere? Thank you.

Re: Omc 3.0 not getting into high rmps in gear in water

copper is fine. Anti-siphon is usually part of the fitting at the tank where the fuel line comes out. Your boat should have had one when it left the factory.

Re: Omc 3.0 not getting into high rmps in gear in water

and here's the master list of issues that can cause your original symptom:
http://forums.iboats.com/mercruiser...ives/list-possible-causes-low-wot-295070.html

only thing to add to that would be an issue with the lower shift cable/ ESA system.

Re: Omc 3.0 not getting into high rmps in gear in water

Back to the drawing board. I have replaced the filter, replaced all of the fuel in the tank with some fresh fuel. I blew the fuel line with an air hose to make sure it is not blocked and cleaned the fuel strainer in the carb inlet. All of this and the same thing is still happening. Can't get out of low RPM's. I have even tried to hook up a different fuel source and still nothing. Can it be the fuel pump? How is it possible that I can get the engine to top RPM's when not in gear but the second i put it in gear it just won't go to hinger RPM's. It work fine with muffs on in gear. Any suggestions?

Re: Omc 3.0 not getting into high rmps in gear in water

Howard Sterndrive said:

and here's the master list of issues that can cause your original symptom:
http://forums.iboats.com/mercruiser...ives/list-possible-causes-low-wot-295070.html

only thing to add to that would be an issue with the lower shift cable/ ESA system.

Click to expand...

I have nothing to add to that- sounds like you have eliminate the fuel -to check fuel pump you can tee a gauge in the carb inlet and look for 4 to 7 psi under load
I'd probably go to timing advance weights and springs next - look to see if weights are stuck/gummed up rusty in the distributor

Re: Omc 3.0 not getting into high rmps in gear in water

misiek said:

How is it possible that I can get the engine to top RPM's when not in gear but the second i put it in gear it just won't go to hinger RPM's. It work fine with muffs on in gear. Any suggestions?

Click to expand...

to rev your engine to full rpm without load takes about 15hp.
to rev your engine to proper wot rpm loaded takes 140hp.

revving in neutral proves your engine can make 15hp. i.e. test is not valuable for diagnosis at all - the sickest engine will do that

you could take 2 pistons out and it will still rev to 5000 rpms unloaded

compression test is a good place to start too.

Re: Omc 3.0 not getting into high rmps in gear in water

I saw somewhere in this forum that changing the points over to slectronic can cause problems with the electric shift, just my 2 cents is seems you tried everything else,


Rich

Re: Omc 3.0 not getting into high rmps in gear in water

Yeah. That was mine concern too. But the problem started before I've switched to electronic ignition. I will play with the fuel pump next to see if that could be the cause. The whole problem started on my first boat outing. Like every spring I got the boat to fire up. Then I took it out on the lake. I was running rough bit I could get it up about 30 an hour, and then at the and of the run it felt like it got cleared up and started running full WOT and the usual top speed. Then I noticed the boat taking on some little water. It was the transom seal. Changed that just like two years prior and took it out and that's when the problem manifested itself. So now Im down to fuel pump or "messed up" engine. I've invested so much emotionally into the the whole thing that it would mess me up now if it will turn out to the the internal engine problem. I still have a spare whole head assembly if it turn out to be a burnt valve or something. This freaking BOAT CARMA gets me every time. By the time I'll get it up and running it will be time to move up to some other dysfunctional UNIT. I have learned so much about this old GAL that it would become hard to let go. The carb is new rebuilt from last year also just for FYI. I actually love the whole set up. OMC 3.0 and the 400 stringer. I think it would be strange to learn new "moves" on anything more recent than that.

Re: Omc 3.0 not getting into high rmps in gear in water

With electronic ignition do the advance weights matter?

Re: Omc 3.0 not getting into high rmps in gear in water

with a Pertronix or similar conversion, the advance weights need to perform exactly the same as they did with the points.
If converting to a Delco or similar electronic distributor, there are no weights.

Re: Omc 3.0 not getting into high rmps in gear in water

OK. I was about to buy a new fuel pump but then I've decided to mess with the old one a bit. First I've checked the engine compression. It was per manual specifications on all cylinders. Then I took the fuel pump off the engine. Took it apart and cleaned it with carburetor cleaner. I saw that the pump was working because it was squirting fuel like 3 to 4 feet away. I've put it back on the engine and sprayed some cleaner into the carburetor and I've also cleaned the fuel line between the fuel pump and the carburetor and it started purring like a kitten. Took it out on the lake and the boat took off like crazy. I've gained 4 mph on my top speed also, which surprised me a lot. I guess the electronic ignition did have something to do with it and most important thing - no more points to mess with! Thank you everybody for your help.