[bostonpilot]

Hi All,

I have a 15hp Mariner (OCxxxx series) that went from running great to feeling pretty sick this season. I have some ideas, but I'd like to get some advice on an attack plan from the knowledge base here. So, I won't pollute your minds with my ideas and opinions - I'd rather get your unbiased advice and then combine that with my ideas. I am about to order parts, so I'd like to come up with a good plan so that I can efficiently and cost effectively address the motor.

First, the symptoms and background. I bought this motor 3 yrs ago used and it ran fairly well, but had a very weak tell tale stream. That winter, I replaced the impeller and the very corroded thermostat (boat is in salt water) which resulted in a nice stream of cooling water. Also, I rebuilt and cleaned the carb (except for reusing the float) and installed new plugs and fuel filter. This yielded a motor that ran very well for the season. This motor is installed on a 25 ft sailboat, so the typical operation is at low rpms in the mooring field, as well as some 50-75% throttle crusing on light wind days to get home.

During the second off-season, I replaced the impeller, zinc, lower end oil, fuel filter and thermostat. This season it started off running well, but approx. mid-season as I left the mooring and throttled up, it sounded as if I was either not acheiving full throttle, or running on 1 cylinder. I returned to the mooring and jiggled plug wires and assorted other appendages and it came back to life and sounded great. Looking at it later on, I think the jiggling of the plug wire was not the solution, just that it happened to come back to life at the same time.

Over the following 2-3 months, I wasn't able to use the boat a whole lot due to a very pregnant wife, so the boat did a lot of sitting without being run.

Near the end of the season, I went to start the motor and it wouldn't start after lots of pulls. Eventually, I was able to get it to start and stay running by shimming the throttle cam follower open a bit with a piece of cardboard, but it seemed to be running very rich. I made an attempt to fix it by:

1 - cleaning off the plugs which were rather black
2 - checking the fuel filter, which was clean
3 - running some sea foam through it, it was a bit smokey, but nothing dramatic
4 - taking her out and running at WOT for 45-60 min. Afterwards it ran fine at WOT, but still wouldn't idle well (made for a interesting time catching the mooring by myself)

A couple of weeks later, I went back out to try again and it wouldn't start no matter what I did. Fastforward two more weeks and it was my scheduled haul date. So, I tried again by:

1 - doing a compression check. both cylinders were ~120ish and equal
2 - changing to new plugs
3 - testing the spark by holding the new plug on the block and hand pulling. There is spark on both cylinders, but it seems like it was a bit of a weak spark. Hard to tell for sure bouncing at the mooring on a very sunny day, but may be weak.
4 - giving it a generous squirt of starter fluid.

The engine started and idled a bit better, but still not well, but now it won't produce full power at WOT. I ran for 2-3 hours this way to get to the storage yard with no change in operation.

I've only spent a few mintues with it now that it is off of the boat and in the house. What I have noticed so far is:

1 - the plug wires are old, but loot ok for the most part. The end attached to the coils seem dirty with some old dielectric grease on them, but they feel secure
2 - when I pull the choke out and the lever depressed the primer plunger, the pluger doesn't rebound up quickly, seems to be a bit gunked up.
3 - a few drops of very dirty black oil/sludge weeped out from the prop hub (don't know if this is related)

So, that's where I am. Have at it. I'd love to hear your suggestions.

Thanks in advance.

[Laddies]

Clean the carb