OMC seadrive V6 225hp not passing 2000 rpms

[Noe.305]

Someone please help me I am about to lose my minds here. I purchased this OMC seadrive V6 225hp from a guy up north who does not even return my calls (now I know why, if he didnt live 450 miles away I would have paid him a visit).

Since day 1 that I took out the boat to the water it never ran past 2000-2500 RPMs, when put the throttle completely open it feels like it wants to go faster but it doesnt. Sometimes after I sit for about 3-4 hours at the sandbar Start up the engine and give it full throttle it goes to about 30-40 mph but after 10-15 mins that the engine warms up it drops back down to 2000-2500rpms. I have spent so much money changing so many different things that its getting to a point where I am getting fed up already. Please help.

I have changed the following items: New power pack, New stator, Disassembled and cleaned & overhauled the complete carb system, New pear pump & hose for gas, New spark plugs, Flushed out the lower unit gears and replaced with new oil.

Please help I am desperate. Thanks

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

What's the model year of your engine?

The most recent models were big bore looper engines with S.L.O.W. or Speed Limiting Overheat Warning systems. They automatically limit the engine to 2500 RPM whenever an engine temperature of 203 degrees F. is reached.

If that is what is happening, the immediate concern is the cooling system, which is somewhat complicated on those engines, but workable.

Start by testing the thermostats and checking that the thermostat seats in the cylinder heads are in good condition.

The tell tale outlet on your motor will indicate that the waterpump is working, but tells you nothing of the circulation of water through the engine's cooling passages.

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

All I know is that several mechanics told me that it a late 80's probrably 86-89. Where can I find out more information for you?

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

If it's the looper engine, it should have a welch plug centered between the banks of cylinders and facing you if you stand at the rear of the boat. The plug is convex and about the size of a nickel. The numbers on that plug may help. There may also be a sticker somewhere on the stern bracket with numbers. The powerpack part number should be visible and that would also help.

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[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

OK Ezeke.... sorry about the delay I just got that information for you... I loctaed that welsh plug which you stated, it is located on the top side of the engine between the cylinder heads it has a part number G3120231, the part number for the power pack was not available I beleive it is on the bottom of the power pack but if you still need that part number I will remove it later today just let me know. Once again thank you for all your help it os greatly appreciated, honestly my boat has ended up in like 4 different mechanics hands they al charge me money plus the parts which they say they replaced and tell me that the problem is fixed when its not.... Just in case another part number that I saw was the part number which belongs to the cylinder head cover which if your standing in the rear of the boat the left side reads 333809-4 and the right side reads 333809. Thank you

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

http://www.crowleymarine.com/omc_sea_drive_parts.cfm

The number on your welch plug is a serial number for your specific motor, which a BRP dealer can deciper, but not me.

The numbers on your cylinder heads are casting numbers, but they go with a 1988,1990, 1991 or 1992 big bore 90 degree looper engine.

I think that the problem that you are experienceing is in the cooling system and is leading to S.L.O.W. engaging when it should not because the cooling system is not working as it should.

There is a shift assist switch behind the shift lever on the starboard side of the engine that could also be causing the problem if it is misaligned.

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

Click the attached thumbnail so that you can see the parts of the thermostat system.

The lower circled area is the water control that is supposed to change the flow of water at 2500 RPM.

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

Just a heads up the thermostats were both removed by a mechanic when he was under the impression that it was that cause. So right now from your diagram the your first red circle on top is the thermostat which were removed and your second red circle towards the bottom you think that it may be clogged or something may be broken there???

Also another mechanic recently advised me that I needed to change the timer base which is located under the stator. He was stating that it sounded like an electrical issue. With your experiance and your knowledge what do you think???

Honestly outside of the water it will go to 5000rpms without a problem but when its under load in the water it feels like it half my engine is dropped.

A compression check was done last year and all six cylinders were all in the 91-94 range.

At this point I am trusting you here in iboats after seeing how many boat owners you have helped.

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

Need more information to be sure, but there are possible ignition problems as well as cooling problems that could cause the symptoms.

Under no circumstances should the engine be running at 5000 RPM with no load on it.

Try disabling the shift assist switch temporarily; it is located behind the shift lever on the starboard side of the engine. You disable it temporarily by disconnecting the black wire that grounds it to the engine block. Be aware that this will make it much more difficult to shift out of forward gear so be careful, especially when approaching docks and other boats.

You can also try temporarily disconnecting the fuel pump wiring harness in case a blocking diode has failed in the harness.

Running without the thermostats is a really bad idea with your engine for two reasons: one is that the big loopers don't run well like that and the cylinders, pistons and rings wear incorrectly because they are shaped wrong when cold, and two, because the engine has a QuikStart ignition which needs to run to a specified temperature before the QuikStart timing advance will release.

It would be much better to perform the necessary repairs so that the cooling system works as designed.

Even with no thermostats, the water control valve still needs to be able to do the job for which it is installed, which is to redirect the flow of water at a specified RPM. It can be removed entirely, but not without changing the thermostat housing.

BTW, if you want a leg up on your wrench, buy the factory service manual
for the 1989 3L Seadrive model 30APRARF from the printer: http://www.outboardbooks.com/index.cfm?fuseaction=search.main

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

What addional information would you need? please advise. Thank you

The shift switch was disconnected aswell.

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

There is a harness running from the fuel pump to the main harness; temporarily disconnect the amphenol plug, three or four wires, and see if there is a change.

There is a single tan wire running from the vacuum switch near the fuel pump. Try disconnecting that temporarily and see if there is a change.

We want to eliminate these as possible reasons for S.L.O.W. to be shutting down half of your cylinders.

If disconnecting either of those results in a change, the blocking diode in the main engine harness may be bad.

You could also use an inductive timing light to see if you have fire to all plugs at all RPM ranges that you can reach.

I will attempt to consider all information that I receive from you, but I can't see much from here.

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

I think that found the problem... If I am right them the problem should be fixed... I thought that the thermostats were removed, I was wrong they you were never removed and they were stuck. I had no water cooling my cylinders, so I beleive that you were correct in saying that I had a cooling system problem. I opened up both thermostats and removed them I left them open and now I have a nice flow of water throughout my engine and it honestly sound different. Now it pisses with force when before it only dripped.
And the other problem that I found was that the spark plug cables all one tiny hairline crack all 6 cables in the same spot which I found out because I got shocked (OUCH). I will change the spark plug cables this week and run the boat this friday morning. Thank you for all your help I hope everything is now fixed and I will keep you posted on friday. Again thank you.

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

Hey Ezeke, I was just testing the boat and I noticed that that the engine was making a snapping noise when it passed 2,500-3,000rpms.... Although it doesnt make the noise when the boat is idleing... Do you have any idea what that noise could be???

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

There is a harness running from the fuel pump to the main harness; temporarily disconnect the amphenol plug, three or four wires, and see if there is a change.

There is a single tan wire running from the vacuum switch near the fuel pump. Try disconnecting that temporarily and see if there is a change.

We want to eliminate these as possible reasons for S.L.O.W. to be shutting down half of your cylinders.

If disconnecting either of those results in a change, the blocking diode in the main engine harness may be bad.

You could also use an inductive timing light to see if you have fire to all plugs at all RPM ranges that you can reach.

I will attempt to consider all information that I receive from you, but I can't see much from here.

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Hey Ezeke, I was just testing the boat and I noticed that that the engine was making a snapping noise when it passed 2,500-3,000rpms.... Although it doesnt make the noise when the boat is idleing... Do you have any idea what that noise could be???

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

Probably arcing off the plug wires. Watch it in the dark, you will be able to see it better.

That's usually from old wire or using auto wire when solid core is needed.

That can also come from cracked insulator on the sparkplugs or improperly fittted caps on the wires.

I like the pre-capped wires that CDI has.

 

[Noe.305]

Re: OMC seadrive V6 225hp not passing 2000 rpms

Ezeke, Do you happen to have the shift switch part number for the this engine & also the wiring diagram for the power pack??? I have a very big feeling that maybe a wire could have gotten switched around... Please let me know... Thank you

 

[ezeke]

Re: OMC seadrive V6 225hp not passing 2000 rpms

The switch and cable is 0583608.