1987 Pro V150 Problem

[firemech048]

Two weekends ago I was out fishing. Motor was running great. I have a 1987 ProV 150. I went to start it to move to another spot and I noticed my water pressure had dropped about 10 psi. I raised the motor and checked for weeds and cleaned everything off. I restarted the motor and still had lower water pressure. I tried to accelerate and motor had lost power and rpm. I could only get about 4600 out of it. Ok so now when I got home I pulled the plugs and did a compression check. I have at least 115 lbs on every cylinder and most over 125. I noticed that the spark plug for number 3 cylinder had some moisture around the electrode. I changed the plugs. Number 3 cylinder is get moisture all the time. I have checked spark and cylinder is firing. I am getting moisture in that cylinder. I removed the heads and can't see any obvious problem. My thoughts are to have heads resurfaced replace gaskets and water jacket covers and try it. Am I on the right track? I am only getting moisture in one cylinder!

[jb123]

Did you check head gasket carefully ?
Did you pull water jacket ?

[rodbolt17]

could be a leaking head gasket or a leaking ex cover or ex plate.

[amahaork]

if you removed heads, take and post here pictures of all cylinder walls. they have to be in Yamaha condition

[TownsendsFJR1300]

Not likely but worth a look while the heads off.

Check that cylinder head for any very fine, hairline cracks between the combustion chamber and the water jacket in the head.

[firemech048]

I have pulled the heads and the water jacket cover on the heads. I will post some pics here shortly. I don't see anything obvious. I have looked for cracks and just don't see anything that sticks out.

[firemech048]

I am taking the heads to a machine shop on Monday to have them checked and resurfaced.

[firemech048]

The center cylinder is the one with the problem. The pic of all three cylinders is the good side.

[amahaork]

thanks g-d cylinders looks ok you were lucky removing head 1987 wasn't any frozen headbolts when reinstalling heads use clean or better yet new bolts most likely it was time to change 30 years old head gasket they deteriorate with time and bolts may loose clamping power resurfacing heads always good. and clean threads in block with soft copper brush on drill gently and clean compressed air clean. Have good torque wrench torque in two steps. and don't touch anodes they ok and they useles

[TownsendsFJR1300]

Unless you cleaned the entire engine up, water passages, carbon, etc that is a SUPER CLEAN engine.

You mentioned you did inspect the head gasket very closely for any failures around the cylinder?

[firemech048]

I took my time and sprayed each bolt with PB Blaster and let it sit overnight before I removed them. I will use new bolts and put never sieze on them. I need to convert the torque spec to foot pounds. I was impressed with cyl condition of the motor too!

[amahaork]

to achieve proper torque Yamaha recommend using motor oil on threads (see shop manual) however to prevent water intrusion past gasket and into threads area it is good to apply thread sealer with teflon on couple upper threads of the bolt, sealing threaded area from water and corrosion

[firemech048]

Thanks for the info!!! I appreciate that!

[firemech048]

I had the heads resurfaced and I have reinstalled them with new head gaskets and water cover gaskets. I torqued in two steps just as service manual calls for. I still am getting a small amount of water in number three cylinder. Is it possible for the exhaust cover to have a problem and allow water into the cylinder? Its not a lot of water but enough to cause it not to fire. I know its on the exhaust side but this thing is driving me nuts! I just don't see any obvious reason for it to be getting water into the cylinder! My water pressure has dropped on my gauge and both happened at the same time so it has to be related. Any help would be appreciated!!! If I cant figure this out then going to go to the dark side and switch to Mercury!

[firemech048]

I pulled the exhaust cover off this evening. I finally found the PROBLEM!!! Big hole in it and was letting water get into the cylinders on the right side! I am ordering the parts this evening and will finally have my boat fixed!!! Thanks for the wealth of knowledge that all of you share on a daily basis!!!!