[brendanp]

I have just bought a used 90's 70HP Evinrude engine. The guy I brought it from told be it needed the carbs cleaning as it was miss-firing at high revs. I stripped them and gave them a good clean out and made sure all the jets were clear.

I put some fresh fuel through the engine and gave it a quick fire up dry with no muffs or water through the system. It started immediatly and idled fine for the 10-20secs I ran it. I then got it hooked up to the muffs and started it again. It then proceeded to start to rev and then die repeatedly. Just as it was about to stall it would fire up and rev up again, it continued to do this over and over again. Water was coming out of the tell tail, but there was a considerable puff of white smoke coming out of the exhaust each time it fired up.

I then left it with no water on the muffs and fired it up again, DRY. It then proceeded to run and idle perfectly again ticking over nicely for the 30 seconds I ran it. Once again as soon as I put the water back through, same problem. Rev then die, cloud of white smoke, then rev again and so on. It did this at idle speed and high revs.

I didn't have a compression tester so cant post those stats here - sorry.

Anyway I pulled the head to check the head gasket and couldn't see any real problem with it, the gasket itself did seem a little warped and there was no significant corrosion around the cylinders just a few rough edges on the outer surface where the water circulates. I have never checked a head gasket before so don't really know what I am looking for.

Are there any other places where water can get in? Is it worth changing the gasket now and seeing if this does the trick. Any advice on the proceedure would be appreciated. I am really stuck with this one and have searched the forums to no avail. Hope someone can help me out.

Brendan

[tashasdaddy]

all i know right now is you need to replace the impeller, before putting the boat in the water.

[jtexas]

15 or 20 seconds is all it takes to seriously compromise the water pump impeller. Don't crank the engine again until it's been replaced.

Smoke is a normal part of running a two-stroke engine.

Post some pictures of the pistons, cylinder walls and head. And spark plugs.

Welcome to iboats.

[brendanp]

Thanks for the quick response guys. I do understand the smoke comment however there is a difference between oil smoke and water smoke. I am almost 100% that it is water smoke. Impeller was going to be changed anyway thanks for the advice.

[brendanp]

Will put some pics up tomorrow, thanks for advice on the impeller.