!961 Mercury 400 Issue

[DeepCMark58A]

So I attempted to do a sea trial with the boat but never left the dock. The motor would start and idle, a little bit of a high idle but it ran. The problem is when I tried to put the motor in gear it would die, the motor would restart easily. While I wait for the new fuel pump parts and carb kits I want to do a compression test. Problem is that it will not be possible to warm the engine up first, I just want to see that there is compression and if each cylinder is close in compression levels. I know I need to pull all the plugs and have the carbs open, do I need to lube the cylinders with fuel or fogging oil? Am I wasting my time doing a cold compression test?

 

[Texasmark]

Yes. Helps. I don't know if 100 or 120 is your low ball number on that engine. Within 10% cylinder to cylinder sometimes is better determination. If it's good, open your low speed jet(s) a little at a time as you attempt to shift and then again when time to punch out and get on plane...if it stutters, open a bit more at a time till it takes the throttle. Put some Sea Foam in the tank to clean things up.....helps compression too by removing caked carbon around rings.

 

[DeepCMark58A]

It was 95 psi on a cold engine, even or very close on all cylinders. I put an additive in the oil/gas mix that I have found to work very well. When I had the boat in the water I did have it idle for 10-15 minutes in hopes it would clear. This motor was rebuilt and then sat in storage till I mounted it. I am sure that the fuel pump diaphragms are in need of replacement, and the carbs will probably need to be cleaned up too. At least I know know that compression is even, and appears to be good.

 

[Texasmark]

I think fuel and rubber rotting/cracking would be your main issues. I'd still run something like SF in the fuel at least for awhile.

 

[DeepCMark58A]

I add additives every time I add fuel, withe ethanol and it's penchant for absorbing water if you use pump gas from a gas station you have to use additives.

 

[Texasmark]

I add additives every time I add fuel, withe ethanol and it's penchant for absorbing water if you use pump gas from a gas station you have to use additives.

Like everything else, there are doubters and there are doubters, but it's their stuff, their money, and their results. I'll take the proven result, time after time....I use 'em.

 

[DeepCMark58A]

Well I brought it in today have the carbs completely rebuilt as well as the fuel pump. Hopefully when it is done it will be trouble free boating.