evinrude 6hp, fuelproblems?

[phralh]

English is not my native language but I'll try to describe my problem as detailed as possible..

I have a 1970's 6hp evinrude that has served me well many years, until recently.. Started with small vibration on and off, and I didn't bother to find out what was causing it right away. When it got worse I checked and noticed that its only running on bottom cylinder when idling (swapping plugs didn't change anything). It will occationaly run on both when opened up to full throttle. I've looked around forums trying to figure out what's causing this behavior and think it might be the fuelpump thats leaking into top cylinder and flooding it? Top plug is a bit wet compared to the other (both got good spark as far as I can tell). Plus the fuelsystem hasn't been working properly for years, with occational bulb pumping being part of the ride.

What I've done so far is removed the fuelpump and yes, a small tear in diaphragm - kit ordered. Removed and cleaned out carb, fixed float setting and checked needle and valve. Decarb done. I only have access to the engine on weekends so I haven't yet been able to refit carb after cleaning.

Until I have fixed the fuelpump (parts still to be delivered), what else should I check? Have done a compression check, but must have done it wrong somehow since I got about 60psi on both cylinders, which seems a little low? I don't know if I dare remove head, think I'll just end up breaking bolts...

Do you think I'm on the right track?

//Fredrik

 

[JB]

Re: evinrude 6hp, fuelproblems?

Good job finding the leaky fuel pump, phralh.

I would not do more until you have the rebuilt pump and the carb reinstalled.

One thing at a time, and testing before any more steps, saves us from a lot of errors.

 

[F_R]

Re: evinrude 6hp, fuelproblems?

Phralh, I think you did a very good job explaining it in English. Probably fewer errors than most Americans would make.

Your torn fuel pump diaphragm is almost certainly the problem. Don't worry about the compression as long as it runs well.

 

[phralh]

Re: evinrude 6hp, fuelproblems?

Thank for your replies! I'm not in any way good with engines, but I'm starting to get the basic stuff.. (lots of knowledge around these boards). Glad I could make myself understood too, always a challange when it comes to technical terms..

You'll here from me again if it doesn't solve the problem!

Thanks!
//Fredrik

 

[mikesea]

Re: evinrude 6hp, fuelproblems?

have you changed your impeller latly.or gear oil.your learnung wonderfully,this is a task to master,dont wait for it to fail,it will

 

[phralh]

Re: evinrude 6hp, fuelproblems?

Don't know if it's ever have seen a new impeller.. About 7-8 years ago it had some cooling problems. I don't think it ever overheated.. I had it brought to a mechanic twice because of that, and it ran great in their testtank. Turned out to be a little missing plate with the intakeholes. Since then I'm always making sure water is passing through. Have felt the block while running and it's not getting hot. Paint is coming off around the thermostate area - is this a sign of previous overheating (it's looked like this as long as I can remember)?

Did change gearoil about three years ago. Engine had been out of the water 2 years before I started working on it this spring. Have used it all summer though.

This weekend I reinstalled the cleaned carb and defect fuelpump to make sure I didn't screw up the carb while cleaning it. It actually ran on both cylinders (and alot smoother too). Still rebuilding fuelpump though.

Also did a compression test and got about 95psi top, 100psi bottom. I guess that the difference might be leaks through the hole where the feulpump is supposed to be?

//Fredrik

 

[Xcusme]

Re: evinrude 6hp, fuelproblems?

I guess that the difference might be leaks through the hole where the feulpump is supposed to be?

//Fredrik

The difference in compression values is no big deal, it's within a 10% difference. The fuel pump 'hole' is behind the piston rings and doesn't affect the compression. The fuel pump diaphram operates off of the crankcase pressures.
The blistered paint around the thermostat could have come as a result of a previous overheat. Severe overheating can cause head gasket failure (head warping) and lost compression, but that doesn't seem to be a problem on your motor. If you don't know when the last time the water pump impeller has been replaced, it's a good idea to replace it and be sure it's working. With compression reading as you posted, there's many more years of service left in your motor , if it's maintained. You might want to change the lower unit lube on an annual basis too. If you did have a water intrusion problem into the lower unit, the water can rust and pit the gears. Annual inspection of the lower unit allows you to fix any leaks and save the gears.

 

[phralh]

Re: evinrude 6hp, fuelproblems?

A little follow up..

I've reinstalled the rebuilt fuelpump and the engine runs great. Now it's reaching higher rpms and is running great on both cylinders. Completely different feel to pump the bulb too. Thanks for all of your input and suggestions!

//Fredrik