69 40hp Pinned at WOT, but wont go fast

[Chrisravosa36]

Alright, Ive had a lot of problems with this motor, pump, lower unit, head gasket and smoke in the cowl. Now when I think I'm done with this, I take it out on the lake and I pin it to wot, and it doesn't move like it should. Only went 10mph max. Wasn't getting on plane. It did start out going only 7 but moved to 10mph. Still was a great time, got plenty of good looks, just would like to get more speed out of her. Also boqt was not overloaded, just a bat, 6 gallons and fishing gear. Here is what I think may be the problem.

1. Wrong prop?
2. Dirty Carb?
3. Fuel pump?


I'm assuming a fuel issue, the prop seems fine, and I don't think that would be the issue, but it's worth a shot.

 

[F_R]

A very common problem, and at least 90% of the time it is because it is running on one cylinder. Remove and ground one spark plug wire and see how it runs. Then do the same with the other wire. Chances are, it will make no difference with one grounded, but won't run at all with the other one grounded. That is the good one. Next step is to find out why the other one is dead.

 

[Chrisravosa36]

A very common problem, and at least 90% of the time it is because it is running on one cylinder. Remove and ground one spark plug wire and see how it runs. Then do the same with the other wire. Chances are, it will make no difference with one grounded, but won't run at all with the other one grounded. That is the good one. Next step is to find out why the other one is dead.

Il do that today!

 

[Chrisravosa36]

A very common problem, and at least 90% of the time it is because it is running on one cylinder. Remove and ground one spark plug wire and see how it runs. Then do the same with the other wire. Chances are, it will make no difference with one grounded, but won't run at all with the other one grounded. That is the good one. Next step is to find out why the other one is dead.

Wait so I ground the plug wire to what? Just against the motor? Or does the inside have to be grounded? Also think it could be the cutoff switch

 

[Silvertip]

If the safety switch was the problem the engine wouldn't run. That switch cannot affect just one cylinder. What is the boat size & weight? Run the engine with one plug wire disconnected and grounded on the engine block. Use a wood clothes pin to hold the wire and to put it back on with the engine running. There should be a notable difference between wire on and wire off. If there is no difference, you found the problem. One dead cylinder. It is also possible the boat is simply too big or too heavy for that motor. Or yes -- a very wrong prop selection. But make sure the engine is providing full power before spending money on props and other band aide measures.

 

[Chrisravosa36]

If the safety switch was the problem the engine wouldn't run. That switch cannot affect just one cylinder. What is the boat size & weight? Run the engine with one plug wire disconnected and grounded on the engine block. Use a wood clothes pin to hold the wire and to put it back on with the engine running. There should be a notable difference between wire on and wire off. If there is no difference, you found the problem. One dead cylinder. It is also possible the boat is simply too big or too heavy for that motor. Or yes -- a very wrong prop selection. But make sure the engine is providing full power before spending money on props and other band aide measures.

I took out both plugs, noticed before I took the bottom one out, there was some oil or some black liquid right below the spark plug hole. Both the plugs seemed black. Another thing I noticed, is that when I first go it, it would idle great in neutral , but now if I put it in it just dies out. I thought the cutout switch cuts spark from one of the cylinders so it doesnt "runaaway" could it be wired wroung?

 

[lindy46]

As I mentioned in one of your other posts, the cut-out switch kills spark in the bottom cylinder in a runaway situation. The center post has a wire going up to the points for the lower cylinder, and another wire going to one of the "M" terminals on the ignition switch. The side post has a wire going to the safety switch (the black plastic plunger thing) and another wire going to one of the small posts on the starter solenoid (ground). It's possible that the cut-out switch is bad which would result in the motor running on one cylinder. You can test the switch using an ohmmeter by applying vacuum to the hose - that should close the circuit. If no vacuum is applied, the circuit should be open.

 

[Chrisravosa36]

As I mentioned in one of your other posts, the cut-out switch kills spark in the bottom cylinder in a runaway situation. The center post has a wire going up to the points for the lower cylinder, and another wire going to one of the "M" terminals on the ignition switch. The side post has a wire going to the safety switch (the black plastic plunger thing) and another wire going to one of the small posts on the starter solenoid (ground). It's possible that the cut-out switch is bad which would result in the motor running on one cylinder. You can test the switch using an ohmmeter by applying vacuum to the hose - that should close the circuit. If no vacuum is applied, the circuit should be open.

Ok, So Im going to take ALOT of pictures when I get home, I followed that diagram, but there was one wire I could not figure out where to put, il get pictures. Also I got some new plugs, JC4/B8S. Gapped to .03. The motor seemed o be running on two cylinders previous to my pulling the head for the gasket intsall. It would idle great in neutral, but now if I put it in neutral, it dies out, even after giving it all the throttle possible in neutral.

 

[F_R]

Actually it is possible for the vacuum cut-out switch to make it run on one cylinder, but the chances are so slim it doesn't even merit consideration. There is a honking big spring in there that holds the switch open unless a high vacuum is applied. When the switch is open, it doesn't do a darn thing.

 

[Chrisravosa36]

Actually it is possible for the vacuum cut-out switch to make it run on one cylinder, but the chances are so slim it doesn't even merit consideration. There is a honking big spring in there that holds the switch open unless a high vacuum is applied. When the switch is open, it doesn't do a darn thing.

But I remeber it running alot better before this, smooth idle ect. I didnt touch anything electrical BUT the cutout switch

 

[Chrisravosa36]

Actually it is possible for the vacuum cut-out switch to make it run on one cylinder, but the chances are so slim it doesn't even merit consideration. There is a honking big spring in there that holds the switch open unless a high vacuum is applied. When the switch is open, it doesn't do a darn thing.

Im not worried that the cut-out switch is bad, Im just worried I wired it wroung.

 

[F_R]

No Title

Do we know what model you have? Nevertheless, the cut-out switch wiring is pretty standard and universal

 

[Chrisravosa36]

40953 I belive, thre some new plugs in it, and surprisingly it ran slot better in the bucket, it actually idled, and didn't due when I brought it down full. The revs where much stronger. The old plug was dark black

 

[Silvertip]

Carbon or oil fouled. Sea Foam is your buddy (although some refer to it as mechanic in a can). You can't use too much Sea Foam so add half a can to your fuel and over a short time, it should clean up any carbon as well as the fuel system.

 

[Tim Frank]

I don't see any mention of whether you actually did the drop test that FR suggested in post #2?

 

[Chrisravosa36]

I don't see any mention of whether you actually did the drop test that FR suggested in post #2?

I dint, but I got a spark tester and did both cylinders, fond that one plug had no spark, changed it and it's bright and clear


Als they where using JS8 plugs in the motor

 

[Chrisravosa36]

If I wanted to try this test, what tool should iuse to take off the boot when running, wouldn't want to get shocked.

 

[jimmbo]

Plastic or insulated pliers

 

[interalian]

I'd want some pretty fat insulation on steel pliers - maybe some 1/2" heater hose over the handles.

 

[jimmbo]

Wear leather lineman gloves