Struggling under load

[robotmark]

I have made the adjustment on my fuel save rod recently, but I’ll take another look.

[Buccaneer]

Does your throttle just start to open when the cam marks reach the pointer?
I’m sure you know, but the cam does adjust .

Prepare to be boarded!

[billw]

I guess I would pull out the spark plugs and look at them. They should appear pretty much the same. I would also check for spark on both cylinders. Spark on that engine should jump a quarter inch, easily. If you’re not familiar with the sound of a running big twin or RD, you can be fooled in thinking that it’s running on both cylinders, when in fact, it’s only running on one. They run remarkably good on one. They just have no power.

Another thought is maybe a bad hook in the bottom of the boat? Just guessing here.

Long live American manufacturing!

[fleetwin]

You indeed may have made the fuel saver rod adjustment, but perhaps the collar loosened up and slid back…I’m sure this issue is something simple, so check the plugs and spark like Bill says.

[robotmark]

Ok great, we’re going to get rain/snow the next 48 hours here in Colorado, but I’ll check the spark once the weather clears and see what happens. Thanks folks!

[robotmark]

Ok, I made some minor adjustments to the throttle, and I put on a new length of 5/16″ fuel line. I used an in-line spark tester and got good spark out of both cylinders, therefore it seems like it wasn’t an issue of running on one cylinder. I put it in the test tank and ran it up. I was able to get wide open throttle and it was *much* faster than it was the other day. My guess it was the fuel line that did it. I’ll put the boat in the water tomorrow to do a real run and see how it goes. Thanks for the all the help everyone!

[robotmark]

OK – so I got it on the water today and it performed very similar as to before. It idles well, starts up right away, sounds good, but under wide open throttle it lopes along, feeling like it’s at half speed. It occasionally lurches at WOT, giving a feeling like it’s slipping gear or cavitating… it’s hard to describe. So now I’m back to square one. Carb is clean, spark is good, fuel hose is good. Back to the drawing board!!

[robotmark]

Also, perhaps it’s obvious, but I’m in Colorado so I’m running this engine at about 5,600 feet above sea level. That’s not considered high altitude around here, but is that something I need to account for?

[fleetwin]

Well, OMC did make high altitude kits for these engines, which included smaller high speed jets… But, you mention that the engine lurches ahead momentarily, so I’m thinking there is something wrong…Does it seem to pick up RPM for that second? I know you mentioned checking spark and it was OK, but perhaps the engine is losing spark to one cylinder at high speed settings…You might want to try using those inline neon testers, then you could monitor them while and assistant drives the boat at WOT. Did you try replacing the plugs again? Just cuz they might be new, doesn’t mean they are any good…
Any chance of you posting a video of the engine misbehaving?

[robotmark]

Guy, I figured it out, and I feel like an idiot. The model number of my engine is 40E71, which is for 15″ transoms. I need an 40EL71, for 20″ transoms. My engine was too short! This model came with a 5″ extension kit which I’ve ordered and am installing this weekend and should be fully in business. Thanks for everyone’s help on this because now my engine is running beautifully.

One final question: when I turn the key to “off” the engine keeps running. Is that supposed to be the case, or should it shut down when I pull the key out of the ignition? Typically I run the throttle down low until it idles off.

[Author]

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