1986 Bayliner 131A Capri Overheating problem

Hi Everyone, I have a problem with overheating at high rpms (over 3000). Within 30-40 seconds after backing off, the temperature drops back to normal.

I have replaced the thermostat. Rebuilt the raw water pump. Removed the heat exchanger and had it acid bathed. It still over heats and there is not much water coming out of the exhaust, very little. The raw pump works great and pumps with a lot of pressure. I also ran the tube that connects to the bottom of the exhaust manifold and replaced that gasket too. While feeling around with my finger up inside the manifold I found it to be a bit corroded but no debris. The boat has always lived in Southern California so it was never winterized. The last thing I can think of is the exhaust manifold. It must be plugged up. My SELOC manual does not address this issue but it does say I can acid bath it if need. Since it is water cooled and the water pressure up to it is very good, it is the only thing left that could be plugged up.

Shortly after purchasing a couple of years ago I had an impeller implode, could parts of the impeller be plugging it up. I did find pieces of impeller in the heat exchanger.

Am I thinking correctly here? Is this a common issue? Does silt and sand not filtered by the screen build up after 20 years? I would think it would blow on out.

Any input is appreciated.

Thanks Guys

Re: 1986 Bayliner 131A Capri Overheating problem

exh manifold could be plugged,i would do a leak-down test on the engine to see if there is a head gasket problem.it is very common on those motors.

Re: 1986 Bayliner 131A Capri Overheating problem

you definately want to get those pieces of the old impeller out of the system.You also might want to open the engine block drain plug(s) on the sides of the block, if it has them. Sand can and does build up in some engine blocks causing a water flow issue.

Re: 1986 Bayliner 131A Capri Overheating problem

if you are running it on the "earmuffs" make sure you have a minimum of 12 gallons a minute water supply. I was running mine on a well and ran out of water capacity after five minutes.

Re: 1986 Bayliner 131A Capri Overheating problem

Have you looked at the water hose nipple on the outdrive? They corrode out and will cause overheating at plaining speeds as they are out of the water at that point. Its located just below the u-joint bellows.