Mercury Sport Jet 90 Starting Problems

[Keehnel1414]

Hello,

I have searched the forum but haven't found any good info yet and was hoping someone could help out or has had this experience.

I just bought a 1993 bayliner jazz with the mercury sport jet 90. When I bought it the seller started the motor with a little bit of starting fluid. I tried starting it today and got it to run for maybe 30 seconds and then nothing after that.

I hooked it up to the flush kit and ran minimal pressure through it. When we pulled the plugs there was a substantial amount of water on the plugs and in the cylinder. We cranked the motor and blew out the water and tried again and the same thing happened again. Water in the #3 cylinder.

I was hoping someone could tell me what is happening with this cylinder.

All spark plugs are firing but I am really worried about the water in the cylinder. You can almost tell when first cranking the motor that it is filling with water as it tries harder and harder to crank. Any help would be greatly appreciated.

I'll post pics tomorrow of the plugs.

 

[Keehnel1414]

Re: Mercury Sport Jet 90 Starting Problems

Hello,

I have searched the forum but haven't found any good info yet and was hoping someone could help out or has had this experience.

I just bought a 1993 bayliner jazz with the mercury sport jet 90. When I bought it the seller started the motor with a little bit of starting fluid. I tried starting it today and got it to run for maybe 30 seconds and then nothing after that.

I hooked it up to the flush kit and ran minimal pressure through it. When we pulled the plugs there was a substantial amount of water on the plugs and in the cylinder. We cranked the motor and blew out the water and tried again and the same thing happened again. Water in the #3 cylinder.

I was hoping someone could tell me what is happening with this cylinder.

All spark plugs are firing but I am really worried about the water in the cylinder. You can almost tell when first cranking the motor that it is filling with water as it tries harder and harder to crank. Any help would be greatly appreciated.

I'll post pics tomorrow of the plugs.

Also tomorrow I am going to test the compression on all cylinders and see if there is an anomaly. That may tell me more. However I was also told that water could come from the exhaust manifold.

 

[Keehnel1414]

Re: Mercury Sport Jet 90 Starting Problems

So I did a compression test today and its not good. Here are the results...

#1 (Top Cylinder) = 119 psi
#2 (Middle Cylinder) = 40 psi
#3 (Bottom Cylinder) = 49 psi

As you can see it is not good. So I am trying to weigh the options of whether or not to rebuild the motor or just clean it up and sell it. What do you think? I am pretty good with tools and could probably do the rebuild myself however, I have never performed a motor rebuild. I found a rebuild kit for $620.00 dollars on maxrules.com.

What do you think would have caused this problem?? If I do the rebuild I want to make sure that this doesn't occur again. Is there anything else that could be wrong with the motor that I don't know about? I was thinking that perhaps the exhaust manifold is bad and that is what is causing it to leak water into the motor.

I was also wondering what this white/creamy colored plastic plug on the head is for? Does anybody know?



If I do decide to rebuild the motor any help would be greatly appreciated. I think I will start a thread during the rebuild and try and help as many people as possible.

 

[lmuss53]

Re: Mercury Sport Jet 90 Starting Problems

If it sat for a long time it could have sticking rings although usually not 2. Try shooting some WD40 or PB Blaster in each cylinder and letting it soak good then retest the compression. It also may be just a blown head gasket. If the pressure is still low after the PB Blaster pull the head off and look at cylinder walls and pistons. The white plug looks like a telltale hole hose could go in there.

I trinker (keyword tinker) with a lot of boat motors and am getting more comfortable with them all the time. If you are not confident in your ability to get this motor apart, diagnose and repair the problem, then get it back together, I would not try to rebuild it. You'll end up with a basket full of parts to pass to the next guy or the junkman.

Repairing it is another story, take it one step at a time, ask for advice along the way and you can probably fix your problem.

Good Luck

 

[Keehnel1414]

Re: Mercury Sport Jet 90 Starting Problems

Hey Imuss, thanks for the reply back.

So after I did the compression test. I talked to my father who is pretty good with motors and mechanical items, not his profession however, and he said the same thing. Shoot some WD-40 down the cylinders to keep from rusting and then I was going to get a head gasket and try a repair on that. I think that will be my determining factor for complete rebuild or just small repairs.

This motor is so small, I think a total rebuild would be pretty easy. Its almost like working on an over sized lawnmower.

The white plug looks like a telltale hole hose could go in there.

Can you explain further what that means? I have looked at my manual and I cannot find any exploded view of the part you described. Thanks for your help.

 

[lmuss53]

Re: Mercury Sport Jet 90 Starting Problems

The telltale is where an outboard motor "pees" to let you know it is pumping water, itmay not be used for the jet, but that is the right spot for the hose to come out of.

I think pulling the head is a good next step and what you see there will lead you to the next step.

 

[Faztbullet]

Re: Mercury Sport Jet 90 Starting Problems

Dont buy anything till you get it pulled apart as you may find the crank and rods damaged from water as previous owner likely new motor had problems

 

[Keehnel1414]

Re: Mercury Sport Jet 90 Starting Problems

So I purchased a new head gasket and a new exhaust manifold gasket from **********. I ordered the parts last Saturday and they still haven't even shipped yet. I was hoping I would get them by this weekend but that doesn't look like it is going to happen.

However I still have a lot of prepping for painting and general cleaning up.

I started this thread...

http://forums.iboats.com/boat-restoration-building-hull-repair/1993-bayliner-jazz-restoration-how-607437.html

To show my progress in bringing this boat back to life. I will get the motor running one way or another. If I have to buy a new crank or perhaps a whole new motor I think I am going to do it. Either that or I paint it and sell it to someone who wants to tinker with the motor. Either way I don't think I could have found a better boat for $800 bucks.

I can really only work on this boat on the weekends as I am living in a hotel and it stays at my warehouse. I am really going to shoot for the final prep for paint and then hopefully next weekend I will be able to tear into the engine. Look for an update on both threads.