Rebuilding 90 hp Evinrude powerhead

[GlasV162]

My 1990 90 hp Evinrude needs to be rebuilt--lost 1/4 of a ring on the bottom starboard cylinder. If anyone can tell me what questions to ask the mechanic, what parts should be replaced when rebuilding the powerhead, and what a fair price would be, I'd appreciate it. Thanks.

 

[funpilot]

Re: Rebuilding 90 hp Evinrude powerhead

I just rebuilt my 1990 90 hp.

I stripped my engine and pulled it off and took the block to a machinist who specializes in aluminum blocks, boat motors and two cycle. He was able to determine that two holes needed boring to .020 over and two just needed honing. He gave me a good price on Wiseco pistons, and machined the engine according. So for a total of about $400 I got my block prepped and new pistions and rings. Ask your machinist to check your holes and your pistons for round tolerance up and down the bores if you can't do that yourself.

I bought my gasket kit, assembly lube, carbon remover and crankcase sealent (get the small tube, it will do one motor) here from iboats. I called them rather than use the website. The NAPA marine catalog has all the same part numbers iboat uses, so you can ask for a copy from them and see the parts before you buy. In my experience, the iboats website is incomplete, but the people on the phone are very helpful. I knew that my sticking rings came from a failure of one of the exhaust plate gaskets, so I wasn't too concerned about the carburetors, but I did go to a local Johnson dealer and picked up some carb kits, the proper spark plugs and a check valve for the gas recirculation system I managed to break off. Total spent on gaskets and the like was $300.

I took the engine off one night, stripped it the next, and then had the machining done. I built it a week later, installed it and then did a link and synch, which I repeated when I decided to rebuild the carbs. Total elapsed time was about four weeks, but I could have done it quicker, but it was early May, so I didn't much care.

The Clymer manual was 'OK' but I hear that the factory manual is better. I scraped and cleaned all surfaces and made sure that everything fit well, and I also pulled my thermostats, and tested them in a sauce pan with a meat thermometer.

What I didn't replace:

The bearings were all fine, so I kept them. If I were doing it for a living I would probably have replaced them. They would have cost about $300.

My thermostats were fine. But I did replace my water hoses.

My fuel pump/VRO was fine.

The crankshaft seals were fine. I did replace the upper and lower o-rings on the upper and lower bearings.

My coils and power packs.

My rod bolts were fine (not stretched)

Hope this helps

fp

 

[Walker]

Re: Rebuilding 90 hp Evinrude powerhead

I just rebuilt my 1990 90 hp.

.



What I didn't replace:

The bearings were all fine, so I kept them. If I were doing it for a living I would probably have replaced them. They would have cost about $300.

My thermostats were fine. But I did replace my water hoses.

My fuel pump/VRO was fine.

The crankshaft seals were fine. I did replace the upper and lower o-rings on the upper and lower bearings.

My coils and power packs.

My rod bolts were fine (not stretched)

Hope this helps

fp

I personally replace rod bearimgs when I do a rebuild. Make your own choice on that.
Tstats replaced for sure. They're relatively cheap.
And no way no how put it back together with the same connecting rod bolts.

 

[GlasV162]

Re: Rebuilding 90 hp Evinrude powerhead

Just wondering.........how did you determine that your fuel pump/vro was ok--is there a way to check while it's removed from the powerhead? Thanks.

 

[Dhadley]

Re: Rebuilding 90 hp Evinrude powerhead

Just make sure you determine, and fix, the cause of the problem so it won't happen again. The most common cause of what you describe is coking. A black sticky carbon like substance. Lugging the motor promotes coking. With motors propped in the low 5000 rpm range it's fairly common. With motors propped in the mid 5000 range, it still happens but it takes longer. Motors propped out at 5800 - 6000, it's pretty rare. It has to do with combustion temps and todays fuel.

 

[funpilot]

Re: Rebuilding 90 hp Evinrude powerhead

Regarding the checking of the VRO pump, it was working when I tore down the engine, as evidence by it using oil in the tank, and the fact that two of the holes were just fine, and all the bearings were in great shape, i.e. the system provides the same mix to all cylinders since it delivers the same fuel to all the carburetors. By running premix with the VRO system on break in, I was able to determine that it was still working when I resinstalled it.

The cause of my rebuild, as I said was a blown exhaust cover gasket which allowed the starboard cylinder head to overheat, coking the rings. You can do a lot to avoid that just by decarbing, and inspecting your engine for leaks, something I neglected to do, even though that gasket had failed before. T-stats are cheap, but mine opened at 145 deg f which is close enough to 143 deg to not matter, so I reused them. Replace rod bolts if you like, but if you can inspect them, and see no stretching they will be no where near their tensile load limit if torqued correctly. The rod bolts held fine for 16 years, if my motor hadn't coked up, they would have continued on for many more years. I reasoned, absent any sign of damage that retorquing them would not bring them to their yield point. Metalurgy hasn't changed much in 16 years.

fp

 

[emdsapmgr]

Re: Rebuilding 90 hp Evinrude powerhead

Why take a chance with a new engine-do the water pump and thermostats. Both are easier to do when the engine is being torn down.

 

[funpilot]

Re: Rebuilding 90 hp Evinrude powerhead

Actually, I agree with both Walker and you emdsapmgr, about thermostats. The housings should get new gaskets, the lift springs should be checked for length and function, and I tested and cleaned the thermostats. I came pretty close to just replacing them because it is a hassle sometimes to examine and clean them. Running in lake water with a constant exchange of water in a boat engine is different than a car engine where acids can build up. On the other hand, you are more likely to get calcium deposits on a thermostat in a boat, which can slow the rate of heat transfer, but not eat the metal on the 'stat, like acids might. If it makes you feel better, replace the t-stats, but if you do, check them first as I've seen plenty which didn't work the way they were supposed to. Since I rebuild old cars, I'm always making the use/reuse decision. I've seen a lot of 'new' parts which didn't function as well as the parts they were replacing. New rod bolts don't guarantee that they have the correct metalurgy, as even reputable suppliers can be fooled by their suppliers. So, if it was working when I took it apart, and it can be cleaned up and examined, threads chased with a die, I tend to trust what I can see. I've either been very lucky, or if I get a failure mode I do it differently the next time. Like I said, if I were doing it for a living, I might cover my butt and replace things at the customer's nickel as well to avoid the warranty work (my nickel).

GlasV162, it occurs to me that you may be planning on having a shop do this rebuild for you. I recommend you look over MasterBrian's excellent thread as he is rebuilding his motor, and that you consider doing this job yourself. You will need a torque wrench, a good machinist, and the ability to stop and take your time if things are not going the way they should. All the other tools, except picking up a 5/16 12 pt socket (< $5) for the rod bolts are propably already in your tool chest. You will have a bit of trouble getting the flywheel off without a flywheel strap (which you can rent), or some other method, but even that can be helped if you ask about it here. Take a lot of digital pictures for reassembly.

good luck,
fp