1985 Bayliner OB Idle Problem

[baybooger]

I have a bayliner 1985 with a big problem. It wont Idle for more than 10-20min. Without the cover it will idle fine in the water but with cover mabey 10-20min. I have done the carbs, fuel filter and ignition and water pump. My mechanic thinks it is the back presure against the gasket on the lower unit pushing exhaust through the seal making it stall. I have never decarbed the engine nor do I know what it is. The engine has 60 original hours and the mechanic says it needs the seal has any one heard of this? Is decarb the first step? What is decard? The reason I ask it about 2k to fix the gaskets.

 

[Frank Acampora]

Re: 1985 Bayliner OB Idle Problem

First get a mechanic who knows the engines and knows what he is talking about. A leaking base gasket simply can not leak enough exhaust gas to stall the engine. Also get a mechanic who is not sending his children to college on your dollars. 2K is the price for a new short block. Replacing the base gasket (which even if it leaks would not cause the problem) should cost way less. say 30 bucks for the gasket and 500 for labor at 100 bucks an hour.

Second, do this yourself: look inside at the back of the engine below the head. Centered inside between the leg and the rear shroud you will see a black rubber bellows. This is part of the idle relief system. The purpose of the idle relief is to vent exhaust and cooling water through the two holes in the back when the engine is sitting low in the water. This relieves back-pressure and keeps the engine from stalling.

If the rubber bellows has a tear or a hole in it, exhaust will enter the engine compartment and eventually build up to the point where the engine does not get enough fresh air (oxygen) to run. Yet with the cover off, it will idle all day.

This can also happen if the bellows is not seated properly in the tapered seat of the back shroud. SO: the first thing you do is to reach down and wiggle the bellows to be sure it is seated correctly. It is cramped and may take someone with small hands. If that solves the problem, then your repair has cost 0 dollars. If it does not solve the problem, look to see if you can see exhaust leaking through a hole or if you can feel a tear. If you can, the bellows needs to be replaced. You can do it yourself. There are three screws on each side of the rear shroud and six screws inside the engine compartment. remove them and wedge the shroud off the roll pins on the bottom. Now remove the hose clamp holding on the bellows and remove it. buy a new one and install it.

Total cost? 20-30 dollars.