89 Mercruiser power issue?

[Flappo]

Hello. I?ve got a 89 Mercruiser 3.7L LX 190hp in my boat. It?s been sitting in it?s slip for the last three weeks with what I believe to be some kind of a ?power issue.? It turns over, but it?s clearly weak. The problem?s been going on for about three weeks and I?ve taken the opportunity to do some trouble shooting myself and get familiar with the engine.

I checked the fuel and that?s not the issue (full tank/tried ether in carb). Both batteries are topped off and on a trickle charger, which is working. I?ve cleaned and reconnected all of the battery terminals (a couple of times)?they?re on there nice and tight. I pulled off the distributor cap and checked the points (solid spark across them). I checked the spark at the plugs, that wasn?t it. I pulled each plug and turned it over (plenty of air spitting out, no water in there). I checked the fuses, all good.

So I was down at the boat waiting for a buddy to come down and help me pull the starter (it looks like a nightmare to get it out of these engines?not sure if I need to pull the heat exchanger off to get it out, or just remove the four bolts?anyone?). While I was waiting, I turned the key and the boat started up. We took it out for a little run and would you believe the boat ran better than it ever did (quiet, clean and without some of the other minor issues I?ve dealt with in the past). Got it back to the slip without a problem, turned it off and let it sit for about 10 minutes and tried to turn it over again. It sounded like the same thing I?ve been dealing with for the last 3 weeks?turning over with clearly not enough power to even get to the spark.

Is it a short? An issue inside the starter? Would it even have started if the starter is shot? Someone mentioned pulling off the cables going to the starter (as well as both grounds going to the engine?if I can find them!!!), cleaning them off and reattaching. I?m going to try that today.

Thanks for any help anyone can offer?I?m still new (couple of years) at this boating thing, and it?s killing me to have the boat just sitting in the slip?

 

[Bondo]

Re: 89 Mercruiser power issue?

Someone mentioned pulling off the cables going to the starter (as well as both grounds going to the engine?if I can find them!!!), cleaning them off and reattaching. I?m going to try that today.

Ayuh,....
That's what I was going to mention,...
Just because you stated you cleaned the Battery Ends,....
Cleaning only 1 end of the wiring, is only 1/2 of the job......

 

[Flappo]

Re: 89 Mercruiser power issue?

funny, hadn't thought of it that way. Thanks, I'll try it today.

 

[Don S]

Re: 89 Mercruiser power issue?

I have see cables that people cleaned up, tightened down on the battery and still had problems. They failed to notice the teerminal on the end of the cable was loose and/or the cable had frayed and broken strands.
New cables and it worked great.

 

[Maclin]

Re: 89 Mercruiser power issue?

Check/clean (or replace) the negative ground connection(s) as well, it is just as important, some do not look at it as a complete loop and focus on positive connections only.

 

[Flappo]

Re: 89 Mercruiser power issue?

Well, I found the grounds (not as hard as I thought it would be). I hit the cables at both grounds and all of the wires at the starter with a wire brush and sandpaper. They all looked pretty good, I was thinking that was going to be the fix but unfortunately it wasn't. The boat did start up on a couple of occasions today (I was down there all day), but more often than not it was just the weak turnover that I've been getting the last few weeks. I'm going to pull the starter tomorrow and have it tested. I'm open to any other opinions...thanks for the help.

 

[Maclin]

Re: 89 Mercruiser power issue?

Have you load tested the batteries? or tried different batteries?

 

[chiefalen]

Re: 89 Mercruiser power issue?

I'm gonna get heat for this but here goes. Run a jumper wire to the positive

side of the coil from the positive side of the battery. With a switch. Have

someone stand bye the switch on the jumper wire. Have the person switch on

the juice to the coil and try and start the boat . First pump the throttle 2 or 3

times before you try to start it. If it doesn't start on the third try shut off

power to the coil via the switch. Do not leave power to the coil, will burn out

the points and the coil.Do not crank the starter for more than 5 seconds at a

time. post what happens

 

[Flappo]

Re: 89 Mercruiser power issue?

Have you load tested the batteries? or tried different batteries?

Yes, they're topped off. I've even thrown an additional power pack on the cranking battery. I just replaced the cranking battery at the beginning of this year. There's also a trickle charger running to both batteries

 

[Flappo]

Re: 89 Mercruiser power issue?

Alright Chiefalen, I'll give that a shot today before i yank out the starter.

Does anyone know if I need to remove the heat exchanger to take out the starter in this engine? Also, is it only the 4 bolts on the front of the harness, or is there a bolt or two on the back?

 

[Maclin]

Re: 89 Mercruiser power issue?

A load test for a battery shows what it does under a load, not the same thing as checking the voltage after charging or just making sure the charger is working. Even a new cranking battery can have a problem. Why did you replace the cranking battery? Did the problem show up at all before the new battery was installed? If not, then you can see where I am going with this. I would take the cranking battery in for a load test first, it should be easier to remove than the starter.

This also makes me curious how the boat is wired for the dual or multiple batteries. Is there a switch? Is there a cranking battery and a deep cycle? Is only the cranking battery wired in and used for cranking? If not then the deep cycle battery can drag down the other under load.

After the load test(s) you will be confident that the problem will not return if all you do is replace the starter.

 

[Flappo]

Re: 89 Mercruiser power issue?

This also makes me curious how the boat is wired for the dual or multiple batteries. Is there a switch? Is there a cranking battery and a deep cycle? Is only the cranking battery wired in and used for cranking? If not then the deep cycle battery can drag down the other under load.

I will try the load test first...didn't know that info, thanks. The boat is wired with two batteries...one for cranking, the other for accessories. Part of my troubleshooting was to replace the battery switch b/c when i looked under it, there was a ton of corrosion. I've checked and re-checked all of the fittings. I'm certain they're all wired to the correct spots also.

It sounds like i should do a load test on the accessories battery also. I replaced the cranking battery this spring b/c it was approximately three years old and was shot. The accessory battery had good cells and was still holding a charge.

 

[Flappo]

Re: 89 Mercruiser power issue?

Long story short, I ended up pulling the starter and testing it. It was fried, so I'm having it rebuilt. Thanks for the help/guidance.