Boat will not go past 2rpms with load

[Brian2009]

Hello, I have a 1969 omc gm 3.0 straight 4, I brought this boat from someone about 4 months ago. The guy I brought the boat from new nothing about it. It needed a new floor and seats. So took it home tryed starting it no spark. So I replaced the coils, points, spark plugs, wires. Then it worked took care of that problem. Then we noticed the boat was not sucking water figured out it need a new impeller so bought a new one of those and that problem was fixed. Then we took it out on the water would not accelerate past 2rpms. It goes to 2 rmps then does nothing. So, we took it home I changed fuel lines, filters, had carbs rebuilt, made sure gap was right and points where correct to book, etc. Also set timing as book said at least I am pretty sure, took the prop off and took it to a prop store to see if anything was wrong with it and if it was the right one, nothing wrong with that. So after all that we took it back out and nothing still does the same thing. In my driveway with muffs on it will accelarte but with load it will not go past 2rpms. You go to push the lever down to go faster and the lever goes down but rpms stop at 2rpms. Out of ideas, Any help?

 

[futz]

Re: Boat will not go past 2rpms with load

compression test.

 

[Brian2009]

Re: Boat will not go past 2rpms with load

Did compression test all good at 150psi

 

[Don S]

Re: Boat will not go past 2rpms with load

Did you have some strange G shaped piece of metal left over after you changed the point?

 

[Maclin]

Re: Boat will not go past 2rpms with load

I came up with the same thought as Don S, your symptom is that of leaving the spring off of the breaker points

 

[can-amsledder]

Re: Boat will not go past 2rpms with load

What you guys are thinking is that the advance in the distributor is not working! You might be on to something! Even if the part it in place it may still not be working!
Here?s what I?d try. Measure the size of your harmonic balancer and buy some timing tape. With the timing tape installed you will be able to see with a timing light if the timing is advancing as it should. Someone correct me here but if memory serves me right it should be about 30 degrease at 3000rpms.

If you are not sure what I mean by timing tape clink on the link.
http://www.summitracing.com/search/?keyword=timing%20tape&dds=1

 

[Don S]

Re: Boat will not go past 2rpms with load

What you guys are thinking is that the advance in the distributor is not working!

Nope, that is NOT what we are thinking. It has nothing to do with timing. If the spring is left off the points, the points will not close fast enough at higher rpms.

 

[can-amsledder]

Re: Boat will not go past 2rpms with load

This is going to sound stupid but I?ll ask anyways. You said the boat need a new floor. I?m assuming you haven?t replaced that yet. What are the chances that the boat (wood & foam) are so water logged that the extra weight is what?s holding the boat back? You did say the boat will rev up when in the driveway.

 

[TurboK9]

Re: Boat will not go past 2rpms with load

Nope, that is NOT what we are thinking. It has nothing to do with timing. If the spring is left off the points, the points will not close fast enough at higher rpms.

Wait... He says boat goes past 2K RPM fine on muffs, but not under load. If the issue is the points closing at high RPM load or not should not make a difference.

Question for OP... How does the prop shop know you pitch is correct for your boat/engine combo? You may have an excellent prop, but be wayyyyy over propped. Do you know what pitch you have?

You say you replaced the fuel pump... check the fuel and vent lines. If your vent line is plugged/kinked you will loose power/rpm under load as you create a vacuum lock in the tank. Take off the gas cap and give her a go. If your fuel feed line is kinked / gooked up, same symptom.

 

[Brian2009]

Re: Boat will not go past 2rpms with load

I talked to my husband after reading the stuff about the points. He said that there was no g like shape after changing the points. Also he said that when he brought the new points there was no seprate spring with them. He said it came in to seprate peices the rotor and points but the points where all one. He said that spring is built into the points.

And yes the new floor and new seats we made have already been replaced, We replace both after we got the engine running because we didn't no we where going to have any other problems. But, he said thats not the problem and there in no foam in it.

 

[Brian2009]

Re: Boat will not go past 2rpms with load

Prop is at 19, prop shop said you cant go much lower so that cant be the problem. And as far as the fuel lines and everything he will have to double check everything again. I will let you know the results of that after he goes over it. Might not be for a couple days depending on how busy we are.

 

[Maclin]

Re: Boat will not go past 2rpms with load

Improper dwell setting will act like that, rev in neutral but not under load. Same with stuck mechanical advance. Also still one of the symptoms of breaker points bounce.

 

[futz]

Re: Boat will not go past 2rpms with load

was there a 3.0 in 69'?

You posted you have twin carbs. I don't see where you test the psi the fuel pump, to see if it's giving you enough pressure.

I would love to see a pic of the motor. outdrive also.

 

[Brian2009]

Re: Boat will not go past 2rpms with load

Maclin what is a dwell setting?

My husband is still at work. I went and took a couple different pics of each. Problem is I am trying to post them and it will not let me, all pics are say that they exceed the limit and I dont know how to make them smaller. The boat registration say its a 1969 penn yan and thats the engine and outdrive that it had. I dont think he checked the fuel pump. Are you saying he has to check the psi of the fuel pump? When he was messing with the boat the only thing he said was he did a compression test and the psi was 150 in all 4.

 

[futz]

Re: Boat will not go past 2rpms with load

and i think you have a 120 hp motor, it does have twin carbs? And yes please have him do a psi test of the fuel pump, and post the result.

 

[marksalot]

Re: Boat will not go past 2rpms with load

I had s smilar problem with my old mercruiser,Im not sure if it was the anti siphon valve?or backflow preventor,It was the ball in the housing right on top of the fuel tank.

 

[Brian2009]

Re: Boat will not go past 2rpms with load

yes it is a 120hp. yep on the twin carbs and can you tell me how to check the psi on the fuel pump and what should the psi be?

 

[Brian2009]

Re: Boat will not go past 2rpms with load

If anyone wants to see pics you will have to e-mail me at Nicolequinn2008@yahoo.com and then I can send you pics of the motor and outdrive. They will not post on here because pics are to big I guess and I dont know how to get them smaller. So that would be the best way to see the pics.

 

[Maclin]

Re: Boat will not go past 2rpms with load

Dwell is the breaker points setting as measured with a dwell meter. You set the breaker points gap to start and then check it with a dwell meter and adjust the gap again as needed to get the dwell in the specified range. Then you adjust the timing.

You mentioned the points were changed, what spec was used for the gap and dwell? Was the person who did that work familiar with tuning a breaker points style ignition?

 

[futz]

Re: Boat will not go past 2rpms with load

you hook a gauge up to the fuel pump and, remove the coil wire from the distributor, so it doesn't start, then crank the motor over 4-5 times and then post the result. But no less then 4 psi no more then 7 psi.

one other thing what temp is the motor running at? oil pressure etc., what i really want to know what else is the motor doing, pinging, surging, got to be doing something?