full throutle it surges and has loss of power

I have a 1958 35hp johnson seahorse it starts fine idels good and at about 1/2 throutle if runs good. However at full throutle it begins to surge and losses power. So far I have changed the fuel pump, replaced points and condesers, setting the points to .020, rebuilt the carb, replaced the gas tank and gas and changed the spark plugs. I have good spark and the compresion is at 120 psi in both cylinders. I was not the one who did the conversion from a pressurized tank to a fuel pump so i am wondering if that might not be quite right. would any one have an idel at what else it might be?

Re: full throutle it surges and has loss of power

Have you tried resetting the high speed needle valve?

Re: full throutle it surges and has loss of power

is it getting hot? almost sounds like it is overheating. is the rpm in acceptable range when running full throttle?

Re: full throutle it surges and has loss of power

What happens if you pump the primer bulb ??

Re: full throutle it surges and has loss of power

had the same problem a while back , real head scratcher of an prob... until it was discovered that one of the reed plates was broken and another chipped.

Re: full throutle it surges and has loss of power

fishfeatures said:

had the same problem a while back , real head scratcher of an prob... until it was discovered that one of the reed plates was broken and another chipped.

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I have been putting that off not wanting to dig into it that far but my thoughts too were going to the reeds as a possable problem. The other thing I was wondering is who ever did the conversion from the pressure tank to the fuel pump may have taken a short cut. It looks like all they did to the crankcase pressure line is cap it off with a short piece of fuel line with a bolt in the end of it and a couple of hose clamps. Does any one know how well those ports have to be pluged i gan see some gases getting out through it.

Re: full throutle it surges and has loss of power

Daviet said:

Have you tried resetting the high speed needle valve?

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Yes i did set the low speed at 1 1/2 turns and the high speed at 1 turn i adjusted the low speed 1/8 of a turn in at a time till it idel great i tried doing the high speed 1/8 of a turn in both directions it seem to make no diffrence. as to how it ran on the high end untill I of course turned it to clossed and it died. Good thought though any others?

Re: full throutle it surges and has loss of power

QUOTE=boobie;3975415]What happens if you pump the primer bulb ??[/QUOTE]

Nothing, When I first started working on this motor it would not start at all pumping the primer ball told me the old fuel pump was bad so I replaced it. While I was at it I rebuilt the carb, changed points and condensers plugs and the gas tank. The old gas tank was in a real bad way as far as rust in the insided. Nowit starts idels great runs at up to half throutle fine but past that it surges.Thanks for your in-put do you have another?

Re: full throutle it surges and has loss of power

unleaded said:

is it getting hot? almost sounds like it is overheating. is the rpm in acceptable range when running full throttle?

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No its not. the impeller is doing its job there is lots of water coming out the back and the engine is cool.

Re: full throutle it surges and has loss of power

Have you done much with checking the timing/electrics? Can't say that I know much about a 1958 motor, but thought I throw a question out there anyway. Good luck.

Re: full throutle it surges and has loss of power

I was dealing with the same problem on my 59 Johnson . Repaired and replaced some of the same parts you did. Did you change the coils and the spark plug wires? I too changed the points condensers,Rebuilt carb. But I now believe it was the sprark wires or the coils that made my motor have no WOT. I also checked the spark issue before doing any repairs. The best way I found is start motor let idle while Idling pull one of plug wires off. If motor dies you know its only running on one cylinder. Put plug back on restart and then pull the other plug wire This will tell if motor is running on both cylinders and not just one. I also took my time in setting the points(.020) and adjusting the two throttle needeles

Re: full throutle it surges and has loss of power

I bought new coils but when i checked the old ones they worked fine putting out a real strong spark i was always told that coils are one of those things that ether work or they don't. as far as timing i set the points to .020 and made sure the woodriff key was still good on the fly wheel however i am not to sure about the mech, advance that links to the carb i don't know alot about that so if some one could fill me in on that i would appreciaete it. thanks

Re: full throutle it surges and has loss of power

They seem to be working fine at half throutle it works fine. I would think if it was shorting out it would do it before that however i will look at it agian. As far as timing the only thing i know to check is point gap .020 and the wooddriff keyon the fly wheel I don't know alot about how to adjust the mech, advance that ties in to the carb, any wants to give a quick lesson I would appreceaite it.