Mercury 75hp 3cylinder questions

[BenbowJ]

Hi
I'm new here and am in Wales, UK and could do with a little advice.

I recently bought a cheap 15" Fletcher speedboat with a Mercury 3 cylinder 75hp Serial number 09636083 engine on it. The boat had been abandoned in a local boatyard with a collapsed trailer, so I took a chance with it as it was very cheap. I'd say that it is about 12/13 years old and it does seem to be in fairly good condition. Whilst the engine ran and pumped water very well, it was obvious that it wasn't running all that well. However I was able to run it up and down the river a couple of times without incident, before taking it off the water and getting the trailer fixed.

Closer inspection revealed a few problems which I have addressed; New Battery, fixed broken carb linkage, removed and cleaned out carbs, done a "link and synch" according to the manual and a compression check.

Compression check showed all cylinders were about 100psi (although I did use a very cheap compression guage and the engine was cold). Can anyone tell me if these readings are OK?

When the engine was running it was reasonably easy to start but needed quite a bit of throttle, but it didn't idle very well and it was difficult to get in gear as a result. This was before I replaced the carb linkage and cleaned the carbs and did a "link & synch". I haven't been able to run the engine since soing this but I'm hopeing that this had improved things.

I'm not sure if there is a problem with the oil level/temp control module though as when I turn the key there is no warning beep. Can anyone advise the best way to check this please.
Also can anyone advise on the year of manufacture for this engine S No 09636083 Belgian made. Also are there any other known problems and pitfalls with these engines that Ii should know about.

Apologies for rambling on but whilst I do have some experience with outboards, I'm not that familliar with Mercurys.

Thanks in advance
John B

 

[carholme]

Re: Mercury 75hp 3cylinder questions

John;

That s/n comes up as:

75 75 3-cyl 9586000 9682499 1990 Belgium

From here:

Mercury 2-takt, 3-cyl, 60 - 90 hp, produktions?r, modellguide

Parts Listing:

75/90 HP (3 CYLINDER) - Mercury, Mercruiser, Force, etc. Parts Lookup

The service manual you require is P/N: 90-13645-2. If you do not have it, send me a PM with an email address and I will send you a copy as well as the owners manual.

You will be well OK with the compression especially as they are pretty equal.

Gerry

PS: If you do have the manual, see Oil Wng Module testing under 3B-7.

 

[BenbowJ]

Re: Mercury 75hp 3cylinder questions

Thanks Carholme, for your help. I wasn't sure if I had the correct manual or not, you confirmed that I do have the correct one, also the engine age ties in with the build date of the hull. It looks like the engine and hull were originally supplied as a complete package. Bearing in mind the good condition of the hull, it gives me a bit more confidence about the mantenance history of the engine.

I got the engine fired up yesterday (hopefully you can view the video). It started first turn of the key and settled down to a steady idle. It shifts into gear easily with no clunking. All I need to do know is to get it launched and set the idle under load and check out the oil warning module. Then go fishing.

So I guess that from an unknown condition purchase I have been lucky :joyous:

Thanks again
JohnB