1984 85hp force lost power after an hour

[KnarfOH]

Today I went out with my 1984 Bayliner with a 1984 Force 85HP engine. After being out and everything running for about an hour or so fully revved and pulling skiers, etc., I then got into a situation where when I revved the engine to pull a skier or tuber, after a minute or so, the engine would slow down considerably. If I let it sit idling for a few minutes or so, the events repeated themselves.. i.e. initially the engine would rev up to full power but after about a minute or so, it would loose power.

I was able to return to the boat ramp, but of course it ended my day early. Since it is getting more and more difficult to get this engine repaired (the local boat marina went out of business just this year) I was hoping for some ideas on what the problem might be before i seek out a repair solution.

Any ideas out there?

 

[foodfisher]

Re: 1984 85hp force lost power after an hour

Fuel. Anything from a plugged pickup tube in the tank to a damaged diaphram in the pump. Venting nonfunctional. Go thru the system step by step. Sparkplugs?

 

[KnarfOH]

Re: 1984 85hp force lost power after an hour

Fuel. Anything from a plugged pickup tube in the tank to a damaged diaphram in the pump. Venting nonfunctional. Go thru the system step by step. Sparkplugs?

Venting is fine. I switched tanks when the problem started so that tank would have a different pickup tube.

Question: When I prime the fuel by pumping the primer pump, it gets firm. I run the engine and I go fast for about minute, then I start feeling the sluggishness again. When I feel the primer pump, it is squishy again. Does this tell me anything? Could a faulty primer pump be the problem?

I will look for a thread on here to check diaphram in the pump. Is that an easy fix?

This is 1984 motor and the diaphram in the pump would be original. I have been running fine earlier this season and for the first hour yesterday. I ran out of fuel in tank #1 and switched to tank #2. The problem started after the switch. I had 3 tanks on board so I switched to tank #3. Problem persisted.

Thanks for your reply and assistance.

 

[john from md]

Re: 1984 85hp force lost power after an hour

There are three check valves in the fuel pump. Alcohol mixed fuel eventually causes them to stick and swell. One of the indicators is the bulb getting soft. Another is the engine running at low rpm and not at high rpm.

The valves are only about $5 a piece but you have to be handy to install two of them. One of them is held in with two screws. You can take a chance and replace the easy one but, even if it works, the others will start sticking soon.

Old valves have a clear or amber disk in the center, new valves have a black or charcoal colored disk and appear to be made of a different material.

 

[KnarfOH]

Re: 1984 85hp force lost power after an hour

There are three check valves in the fuel pump. Alcohol mixed fuel eventually causes them to stick and swell. One of the indicators is the bulb getting soft. Another is the engine running at low rpm and not at high rpm.

The valves are only about $5 a piece but you have to be handy to install two of them. One of them is held in with two screws. You can take a chance and replace the easy one but, even if it works, the others will start sticking soon.

Old valves have a clear or amber disk in the center, new valves have a black or charcoal colored disk and appear to be made of a different material.

Are these the parts I need?
http://www.iboats.com/mall/partfinder/?*******=806091973&gd_grid_id=125&gd_poid=112435&gd_row=25&**********=197692989

 

[john from md]

Re: 1984 85hp force lost power after an hour

No, that is the fuel pump diaphram and gasket. You need item number 8 on the following link

http://www.boats.net/parts/search/M...6X5L/CARBURETOR (BOTTOM JET STYLE)/parts.html

You should also replace the fuel pump diaphram anyway if you don't know how old it is. It would be a shame to get stuck for a $5 part.

 

[KnarfOH]

Re: 1984 85hp force lost power after an hour

No, that is the fuel pump diaphram and gasket. You need item number 8 on the following link

http://www.boats.net/parts/search/M...6X5L/CARBURETOR (BOTTOM JET STYLE)/parts.html

You should also replace the fuel pump diaphram anyway if you don't know how old it is. It would be a shame to get stuck for a $5 part.

First, thanks to everyone that replied. I was getting air in the fuel line. Apparently the o-ring in the female connector was bad and it was sucking air. I had already replaced the fuel line (which was the original) and the primer bulb but had not replaced the female connector because it was crimped in. I did order one on line (less then 5 bucks) but it had not come by today so I bought one at the marina at 4 times the cost, i.e. almost 22 with tax.

I did order the fuel pump kit with the 2 diaphrams and they should be here any day. All of the current parts are the original so getting advice to replace them makes sense. Until I was told to do that, I had never even thought to replace them. Silly not to since they are relatively cheap and I have probably only invested around $200 or less on this boat since I bought it new in 1984.

I see where the one diaphram goes (just behind the metal piece that the fuel filter attaches to). Where does the second one go?

Anyone able to send me those pages out of a service manual or the entire manual?

Lastly, I did not order the part described in the link above. With the boat back to running great I figured I didn't need to.

However, even with a great running boat, I am open to suggestions on what preventative repairs I should make to avoid being stranded at sea.. or in my case the state park near my home.

Thanks again to everyone for their advice.