1987 90HP V4 Johnson overheated... What to replace?

[ztrain727]

Hi Folks -

Was trying to get our small houseboat off the beach the other day and stupidly overheated the motor in reverse at around 4k RPMs. It didn't stall out but was seized when I tried to restart it. Grey/black smoke and smelled like a BBQ. Upon inspection I melted some plastic wire brackets but thankfully nothing major. Fogged the engine and it turned over smooth with the plugs out. Haven't tried cranking yet because the battery didn't have enough juice.

What should I replace? So far I have ordered:

New water pump kit 18-3392
New head gaskets 18-2956
New thermostat kit 18-3673
I plan to use 3/8 OD fuel line for diverters as suggested on this forum.

This motor normally rarely gets above 2k RPMs so it hasn't overheated in the past even though the impeller is probably overdue. The bottom port side cylinder appears to be leaking oil from the head gasket, and now that I overheated it, I better replace them.

I've found videos for replacing the impeller but any info on the head gaskets or thermostat would be great!

I've read this thread specifically on the head gaskets: http://forums.iboats.com/forum/engin...et-replacement

 

[emdsapmgr]

When you have the head gaskets off, make sure you check the 4 rubber water diverters (one per cyl.) Sometimes they restrict water flow around the head if debris lodges between the diverter an the side of the block. Also, When you have the thermostat housing apart, make sure the two pinholes are open in the valve body. (Yours is a later model and may only have one hole) If that hole plugs up, the engine will overheat a idle, even if you have a strong telltale.

 

[emdsapmgr]

The left diverter is "normal" the one on the right is out of position.

 

[ztrain727]

Thanks! Any other gaskets I need when removing the heads?

Any tips for removing the head bolts problem free? I've got and beaker bar and impact driver. Not sure if one would be better. People say to tap the threads... Is that really necessary and if so what size tap?

Thanks

 

[jimmbo]

Before you go and spend any more money, take the bypass covers off and look at the pistons thru the intake ports. You are probably going to see scuffing and scoring on the piston. If so, nothing short of a rebuild is going get the engine running properly.

 

[ztrain727]

Yep, I'm afraid things aren't looking too bright. Tried to crank the motor yesterday. It would start but just barely and when revved it would die. There was a clicking sound. I figure I might as well pull the heads and inspect the pistons and cylinder walls.

How long does a full rebuild take? Is a hoist essential?

 

[interalian]

Rebuild takes as long as the shop quotes. If you do it yourself, longer (mine took 3 months partly because I'm 'detail oriented' and had some shop delays). You can pull the powerhead off by hand - much easier if you've already pulled the heads and flywheel. It's about 80 pounds stripped down.

 

[Bosunsmate]

If its not a salt water motor so the bolts that hold the powerhead down come off easy then you can rebuild it pretty quickly.
A ful day would do it easy. If the bores arent too bad i just use some light sandpaper to get out any tiny gouges and i also run the head on a plane of glass with sandpaper on it to make sure its smooth.
If its just rings to replace its an easy cheap job just make sure you take lots of photos so you know where everything goes

 

[F_R]

Nobody mentioned the exhaust cover gaskets. They need to be replaced whenever a motor is overheated. While you have the covers off you can see the hottest sides of the pistons & rings for scoring. They probably are.

 

[ztrain727]

No Title

Thanks for the info guys...

Popped the heads off and it's not pretty. Top right cylinder has some pretty nasty scoring. There is no machine shop where we live and most of the mechanics have recommended just swapping. Curious to hear your feedback.

 

[interalian]

Looks like aluminum transfer from the piston. The cylinder wall might not be that bad. There's an acid you can use to remove the aluminum - sombeody will chime in with the correct one as it escapes me at the moment.

 

[fish till ya bleed]

hone it mic it then bore all cyd's to next oversize piston

 

[jimmbo]

hone it mic it then bore all cyd's to next oversize piston

Honing is done after boring

 

[ztrain727]

Worth it? I've been told a full rebuild cost $3k where's a new motor is 1k

 

[interalian]

1K for a new motor? FWIW, I put $1400 into my rebuild, doing all work myself except the bore/hone.

 

[ztrain727]

"New" as in running. I suppose $1400 is about a break even. Maybe I'll pull it off for now and get to it this winter. This is prime season out here so time counts on this.

Any chance I could escape with just a hone and re-ring?

 

[interalian]

"New" as in running. I suppose $1400 is about a break even. Maybe I'll pull it off for now and get to it this winter. This is prime season out here so time counts on this.

Any chance I could escape with just a hone and re-ring?[/QUOTE]

Doubtful. If you can get a runner for a grand then rebuild yours properly and sell the runner? Up to you.

 

[Bosunsmate]

"New" as in running. I suppose $1400 is about a break even. Maybe I'll pull it off for now and get to it this winter. This is prime season out here so time counts on this.

Any chance I could escape with just a hone and re-ring?

Depends how deep the grooves are, its looks a bit messy but if thats just slght surface stuff then sure hone and go for it. Ive done it on many motors, even some with decent sized gouges, sure you wont get optimal compression but itl run fine and get you back on the water at minimal cost. Probably cost about $150 for gasket set and rings and a second hand piston if needed
Ive probably done it up to about 1.2mm deep and its still going well on that V4 two years on

 

[fish till ya bleed]

Honing is done after boring

Hone it to clean it up then mic it to find out it is oversize then bore and hone to size for the next oversize piston

 

[jimmbo]

Hone it to clean it up then mic it to find out it is oversize then bore and hone to size for the next oversize piston

You might be honing it for days if the scoring is deep. A machine shop would be able to measure the damaged bore and determine if it is usable