1988 88hp Evinrude exhaust cover

[88olympic]

Hi everyone, I was wondering if someone can help me on an 88 Evinrude. I noticed that the exhaust cover was leaking a little on the bottom today while I was at the dock idling, three blots on the bottom look rusted (paint removed).. It runs perfect no complaints just checking it out after rebuilding the carbs and adjusting the idle. It looks like it could have been leaking there for a while. Well I was going to take the cover off and replace the gaskets and twisted off a bolt. I think that that won't be the last one to twist off, all seem pretty tight for 1/4" bolts. Should I just forget about it and let it leak or can I do some damage to the motor? I really don't want to remove the power head to drill out the bottom bolts. I suppose I would put heat on them and do everything I can to get em out or at least break them off above the threads to get vise grips on em. What do you experts think?

 

[emdsapmgr]

Slight leakage from the outer exhaust cover is common on high hours (old) crossflows. Years of the engine going through hot/cold cycles (normal running) will tend to loosen up the clamp load on the exhaust cover bolts, as the gaskets drys out and shrinks with age. You may find the engine will continue to run just fine with a small leak. You need to keep an eye on it, in case the leak gets worse. If the clamp load on the outer cover permits visible leaks, it is possible that water could start leaking into the exhaust chest past the inner exhaust cover. Once water leaks under pressure into the exhaust chest, water can get forced back in to the cylinders during the combustion process. That's when the real problem starts. Water in the combustion chambers will put out the spark plug fire and can introduce water to the shiny parts of the rotating assembly. That's when you need to get it fixed.

 

[88olympic]

Thanks for the reply. I have decided to fix it now. After much heat and PB blaster I am down to two bolts to remove. I have 4 that are broken off at the plate and should be able to get with vise grips and more heat and PB. Of course the middle one on the bottom row #5 broke off and it looks like it is deep, Maybe an angle drill motor can drill it out without removing the power head I'll see after plate removal. Thanks again, and wish me luck.

 

[emdsapmgr]

When you have the inner exhaust cover off, check it for porosity. It's probably ok, but I've seen them have pinholes in the them and leak water into the chest. You can shine a light from behind it and see if you can see any light through the casting. Also, lay it flat and put water on it. See if any leaks through it.

 

[88olympic]

will do.

 

[88olympic]

emdsapmgr, I ended up breaking off 7 bolts total and am down to 2 left to drill out and re-tap. I will have to replace the bolts and would like your opinion on using stainless, the stock ones were not and I am glad they weren't. The number 3 cylinder exhaust port looks to be cracked, not the cylinder liner though. I will just put it together like this and hope for the best, but I was wondering if you have ever seen or heard of this before? I tried to upload photo but could not. Everything else looks real good.

 

[F_R]

Stainless bolts actually seize from corrosion worse than steel ones because there is more dis-similarity in the metals. Worse, when they do seize and you break them off, they are much more difficult to drill out. Resist the temptation to use them.

 

[88olympic]

F_R, Thanks, any idea about the cracks? they are in the two parts that separate the three ports.?

 

[emdsapmgr]

It's not uncommon for the exhaust/intake bridges to crack between the ports. This usually happens when the engine is severely overheated. (could be by a prior owner) When the piston gets too hot it can actually lock up in the cylinder (when running) due to overheat expansion. When this happens (the piston swells so much) it can damage the fragile exhaust bridges. When one of mine locked up it broke both the aluminum casting and the cast iron cyl liner. My block was scrap. I'd double check the liner bore from the inside just to make sure it's still in 1 pc. You might be able to nurse a few more years out of it.

 

[88olympic]

I rotated the pistons to look at them before putting the cover on and number 3 piston is really chewed up on top, real bad pits, I can put a .015" feeler gauge between the ring and the groove. Not going to put any money into this old motor. I am just putting it together and run till it blows. It's funny that it ran so good.

 

[racerone]

Some folks refuse to accept the fact that these motors break piston rings all the time.----But these motors are easy to rebuild.---A cost effective way to get a like new motor.

 

[88olympic]

Thanks, I will think about it....

 

[emdsapmgr]

These old V4 crossflow engines were prone to throw the top ring on a piston. When that happens, the engine really needs a teardown and overhaul It is acceptable to bore out and just replace one piston during an overhaul. You should consider that you need to hone and replace the 3 ringsets on the other pistons at the same time as you do the (4th) damaged one.

 

[88olympic]

Ya, but the cracks in the exhaust ports are not going to go away.

 

[racerone]

But, but they built thousands of these motors year after year.--Used parts should be available cheap.---Used parts motors are available cheap.---I guess your location may matter.

 

[emdsapmgr]

He mentioned that the exhaust port crack was in the aluminum casting of the block, not in the cast iron cyl liner. I'd be inclined not to rebuild this for that reason. However, as long as the cast iron liner is not cracked in the bridge area, it may be possible to squeeze additional year(s) of service out of that engine. That exact point will be the weak point of the overhaul.

 

[88olympic]

I am going to put it back together and run at least 40-1 mix and baby it. I just use it to run a little ways to the fishing and crabbing grounds in Puget Sound (maybe 3 miles). I can always get home on the kicker. I agree with emdsapmgr, I can't justify rebuilding it with cracks in the exhaust ports. I also see more pits in number 4 exhaust port, Kinda looks like there was sand left in the casting. One of the screw holes on the bottom of the exhaust cover is missing a chunk right where the original leak was. I put JB weld to build it up, it is a small area. I wish I could post a few pictures but it says file is too large. I really love this forum and respect all the members reply's. Thank you all.

 

[racerone]

???----I do not believe they use sand when casting these blocks.

 

[88olympic]

ya, I don't know how they do it. But there are some pretty deep pits. I forgot in my last post that i will check compression probably next week when I test it. Last year it was 115 in #'s 1,2,4 and 105 in #3. It will be interesting to see how it compares now.

 

[88olympic]

Just n update for anybody interested. Looking at my old records I was wrong, last compression was May of 2011. Results were #1-115, #2-115, #3-105 and #4-107. Just checked again today. The results are as follows, #1-110, #2-115, #3-100, #4- 107. I can't believe that this motor runs as good as it does. For how long who knows. These pistons could have been like this for some time, I have run it quite a bit since 2011. I'll be fishing in the lake for a few month's before going out in Puget Sound.