1971 1150 Engine Trouble

[jamnajar]

Here it goes: I got a 1970 "Marine Services Unlimited" boat that came with a 1971 Mercury 115hp engine. (ser.3112641)
http://orangecounty.craigslist.org/boa/398933606.html (no I didn't pay 2k for it)The first thing I did is buy the shop manual. I did a compression test and got (top to bottom) 90#,104#,100#,115#,117#,118#. I tested it cold. Someone told me I should have done the test with a warm motor. Will that really make a difference? and will I have to buy an oversized pistons on the rebuild? (I havent been able to find any)This is my first boat with an engine...

The boat has a water pressure gauge and it reads about 4#s at idle and mabye 6#s at WOT. (well I don't think the throttle cable is adjusted correctly and I feel it was mabye 80% if that matters)

The boat kind of "clunks" into foreward and reverse is that normal?

I am missing the front crest piece on the engine cowl. What is the correct term for this piece and where can I find it used? Thanks in advance!!

PS: anyone have a flywheel puller for rent? or 6 ring compressors?

 

[Chris1956]

Re: 1971 1150 Engine Trouble

Your compression is OK except for no 1. Run some decarbonizer (Seafoam) thru it, and maybe it will get better.

Why do you want to pull the flywheel? Only the battery charging stator is under it, and it may be accessed by removing the 8 5/16 fine thread red painted bolts in the center of the fluwheel.

The missing piece you refer to is the front cowling? See if you can get one used. Most inline sixes will have one.

 

[Chris1956]

Re: 1971 1150 Engine Trouble

BTW - Your water pressure is normal. As for the clunking, see if the idle RPM can be adjusted to 800 RPM or less in neutral. This will be better on the lower unit.

 

[jamnajar]

Re: 1971 1150 Engine Trouble

Thanks for the responses. I am`going to go get some seafoam today and we will see how that goes.

oh, and I was thinking about rebuilding the powerhead....(would need a fywheel puller) But I will try the decarb first.

 

[jamnajar]

Re: 1971 1150 Engine Trouble

I picked up a can of Seafoam and followed the procedure in the FAQ section. The following are the before and after for each cylinder: (#1:90/100, #2 104/120, #3 100/114, #4 115/121, #5 117/131!!, #6 118/126) Needless to say I am more than happy with the results! The boat smoaked like a bastard but now it appears to run better. I am going to take it out saturday, to sync the motor and run the crap out of it. Thanks for the reccomendation!

Also I lowered the idle RPMs and the "clunk" is way quieter.