Mercruiser 3.7 distributor & fuel pump questions

[gw204f]

Picked up 1986 Grady 227 w/a last weekend that had a bad fuel tank, so I wasn't able to run the 190 HP Mercruiser 3.7 that is is powered by. The previous owner had it for 17 years and I was able to speak to the mechanic that has been maintaining it for the past few, so I was pretty comfortable purchasing it w/ out hearing the engine run.

Flash forward to this weekend and I made my first attempt to start it up. Checked the oil and had to drain some to get it to the proper level. Pulled the plugs and reset the gap. Cleaned the flame arrestor. Installed a new fuel filter. All of that looked pretty good. Now the not so good...

I took off the distributor cap to inspect/clean the contacts on the rotor and cap itself. Upon doing this, I noticed that the rotor appears to be hitting the cap slightly. My first thought was someone had installed the wrong rotor, but I've pretty much abondoned that idea. Reason being I can grab the rotor, pull up and get nearly 1/8" of up travel on the shaft the rotor sits on. The rotor doesn't move on the shaft and the distributor housing is solidy mounted. I did a little reasearch and I think this is referred to as "end play" and the amount I have is definitly not normal. There was talk of installing shims to bring it to an acceptable range, but I think mine it way to out of whack to be fixed with washers. Any thoughts?

Despite the cap/rotor issue, I decided to move on with trying to start it. So, I hooked an external fuel tank to the inlet on my water separator, and pumped the ball to move fresh gas up to the carb. I made several attempts to start it, and could never get it to fire (I think I may have flooded it w/ the primer ball). Time was limited so I didn't do any investigative work, but I did manage to find fuel leaking from the fuel pump. Out the battery came... Does anyone know if the fuel pump can be rebuilt?

Thanks.

[spareparts]

its normal for those distributors have some end play, pull it out and check it, if it needs it, shim it up, you can probably repair the one you have faster than finding a replacement. Moroso or Mr Gasket have distributor shims for Delco distributors. I've taken old distributors apart to get the shims. Does it have an aftermarket electronic conversion, if it does, you are supposed to shorten the rotor on some of them. Fuel pumps are available form Sierra and Carter, look at ebasicpower.com for parts

[gw204f]

Thanks. I'll check those shims out. No electronic ignition on this one. It's still running the points setup.

On a side note, which oil would you recommend for this old thing? Merc's 25W-40, or something like Shell Rotella T1 SAE30 or 40?

[spareparts]

Rotella SAE 40. The oil pressure will drop a bunch when its hot, those engines don't use cam bearings, the cam floats in the aluminum block, once it gets hot, the clearances open up

[gw204f]

Thanks again. Mind if I run something else by you?

Checked compression this evening. Cylinders 1 thru 3 were 150 give or take a few. Cylinder 4 only pumped up to 42. I checked it like 6 different time with 2 different gauges.

So, I added a tsp of motor oil to the cyl, rechecked and there was no change. This was the first wet compression test I had ever attempted so I wasn't sure how much oil to use. Been doing some reading since and I don't think I used enough.

Anyway, I ran it again for probably 10 minutes and let it get good and hot. 1, 2 and 3 each came up about 5 psi. 4 came up 50 to 92.

Still not quite sure what all this means. Oil doesn't appear to be contaminated w/ coolant. I did note what looked like some rust on the number 4 plug though.

The longer I let it run, the smoother it got. She definitely loses power when you pull the plug wire to that cyl, so it IS contributing.

Took a few videos of it running.





The oil pressure guage was jumping between 40 and 60.

Any thoughts?

Thanks again for your help.

[step up here]

Where did you get that wide 3.7 and skinny outdrive ?
was that a cell phone camera?

[spareparts]

No improvement from the oil indicates the rings are OK, you've got valve seat issues. You've probably got a leaking riser gasket allowing coolant to leak into cylinder # 4. Look at the gasket between the riser and the manifold, one side should be scalloped between the bolts, the other side should be straight, if its scallop on both sides, you have the old style "bad "gasket. Figure a head job, Not too difficult job, cylinder head will have to go to the machine shop

[reelapeelin]

Originally Posted by step up here

Where did you get that wide 3.7 and skinny outdrive ?
was that a cell phone camera?

Click on the wide 3.7...

[gw204f]

Took those vids w/ my iphone.

Thanks for the info spareparts!

I am going to try and take another set of dry/wet compression readings on cyl 4 tonight simply because I'm not convinced I did my first wet test properly. This time I'll use a tablespoon of oil and give it a little more time to flow down into the rings.

I'll take a look at the riser gasket as well. Sounds like it's a common issue. If that does turn out to be bad, could I just replace it for now and wait until the offseason to have the valves redone?

Thanks again.

[spareparts]

better off to fix it now than wait, its not that hard of a job, biggest wait will be with the machine shop