1986 90HP Evinrude VRO- my first rebuild project

After purchasing a motor for my Starcraft 18ft Holiday, I will be attempting to disassemble and rebuild the powerhead, rebuild carbs, etc.. But I want to do this the right way and have a strong dependable motor to last for years to come. So here is my first post to a new thread. I will certainly have some questions and welcome all the advice I receive from experienced rebuilders reading this forum. I will post pics also as I go through the different activities. Should be a fun project. I am on a budget so this may take some time to complete, but hopefully not the entire season. Thanks for all replys and interest in my project. I will definitely need some guidance from you all as I go along......

1986 90hp Evinrude VRO
Model: E90TLCDC
Compression: 120;120;70;130

Should I just start dismantling and cataloging the parts as I remove them? Im expecting to start with these approximate expenses and needs. Am I missing anything.?

1. OEM Manual - $80
2. Rebuild kit - $7-900
3 Carb kits - (havent priced them yet)
4. Cylinder Bore/Hone/Chamfer - $200
5. Miscellaneous Parts.....$???

Sorry, I accidentally edited my post when I added an image of the bad cylinder. Anyhow, I look forward to all advice from all the experienced people on the forum. My replies and updates may take me a couple of days after replies if my work schedule keeps me busy. Thanks

Re: 1986 90HP Evinrude VRO- my first rebuild project

why do you want to disassemble and rebuild the motor??

is it in need of a rebuild even ??

Re: 1986 90HP Evinrude VRO- my first rebuild project

Hi Fishfeatures: The compression is very low in the #3 cyl. After inspecting the top of the piston, I notice metal shavings. The scoring catches my fingernail so its not something I could just hone (??? maybe). With all the metal flakes I saw, I thought it would be best not to chance more damage to other parts of the engine if I ran it. Everything other than that one cylinder looks good. Compression is decent on the remaining cyls also. I forgot to mention, I will also replace impeller, etc.. Would like to determine how the one cylinder was damaged. Seems to me it was running lean which would mean the VRO is bad or the carb was the cause...or combination of both. I prefer to mix my fuel, so I will also remove the VRO pump and replace with just a fuel pump conversion. Thanks for the reply.

Re: 1986 90HP Evinrude VRO- my first rebuild project

I never copped the compression figures above.:facepalm:....well a rebuild is coming your way, just don't fall into the VRO went bad camp (if it did all cylinders would show signs not just one), maybe it was a blocked carb. Anyway you can keep the VRO pump and use it as a regular one, just block the oil intake pipe just before the pump , disconnect the wiring and then just premix in the tank, no need to buy another pump.

Get the proper OEM manual, take as many pics as you can during the teardown. As for a rebuild kit , i think it's Fatzbullet on here who i believe offers a good deal on rebuild kits maybe he'll chime in here on that.

If you feel comfortable enough then you can tearing it down now, and if you get stuck just ask the guys here , they are very knowledgable and only too willing to help folk out..

Re: 1986 90HP Evinrude VRO- my first rebuild project

You can overbore one cylinder and replace just one piston, up to .030 over- and still run your stock carbs. Make sure you use a matched factory oversize piston as a replacement, so they all weigh the same. You'll need all 4 new ringsets. Do an autopsy on the carb throat that fed the bad cylinder. Likely you have debris in the main fuel jet on that throat, causing a lean condition and the eventual damage to that cyl. Bombardier makes a complete gasket set for engine overhaul.

Re: 1986 90HP Evinrude VRO- my first rebuild project

I've heard about repairing the one cylinder, but seems if I must tear down everything anyway in order to replace the rings, I may as well make each cylinder the same bore....but I like saving $$$ too.

Would the engine have the same durability/reliability? Will the compressions still be acceptable and equal with each other afterwards? Seems the rebored cylinder may become stronger than the others after the fix (then again, I'm not sure since this my first rebuild).

Re: 1986 90HP Evinrude VRO- my first rebuild project

I also removed the front carbs cover. Immediately, you can see there was a problem with the flow of fuel. All of the fuel supply throats were shiny with fuel except for one....the #3 cylinder supply. Attached is the photo. If you look at the lower left supply you can see how dry it looks compared to the other 3. It would appear that fuel/oil was either completely blocked or at least way too lean causing the cylinder to run dry and score the inside of the cylinder.

Re: 1986 90HP Evinrude VRO- my first rebuild project

If you plan to rebuild this and overbore one cyl, your machinist can measure the taper and ovalness of the other 3 cyls. All 4 of them will need to be honed anyway. You both can then decide to do one or all 4. Tear down that carb and look for a restriction, esp on that bad looking side/throat. Once you find the real cause of the problem, you are ready to proceed with your planned repairs and eventual reassembly.

Re: 1986 90HP Evinrude VRO- my first rebuild project

Is honing a cylinder the same as making the cross hatching?? Sorry to be naive, but I'm learning....better to plan out my attack ahead of time...

After boring, does it need additional honing on top of that and then the cross hatching?? Also, do I replace with an oversize piston or is it standard piston with oversize rings only in the bored hole? Thanks again

Re: 1986 90HP Evinrude VRO- my first rebuild project

Usually when the machinist overbores one hole, he will complete the job by honing it. Then that cyl is ready for a new piston. You need to hone the other three so that the cross hatch matches that first cyl, prior to rebuild. When over bored, a new factory oversize piston will come with new oversize pistons in the box. You'd then need 3 sets of standard piston rings for the other three pistons. You'll need to clean up the other pistons, paying special attention to the ring grooves. (Remove all the carbon from the piston and ring grooves.)

Re: 1986 90HP Evinrude VRO- my first rebuild project

How does one determine the size piston and rings after boring the cylinder? If its oversized .020 for example, what is that based on? Is it .020 over standard factory bore, or .020 over what the damaged cylinder is measured to be just prior to boring? Just trying to understand the process so i don't feel so blind when handing over my power head. Do i need to provide std measurements to the machinist or should the marina already know? Thanks again

Re: 1986 90HP Evinrude VRO- my first rebuild project

How does one determine the size piston and rings after boring the cylinder? If its oversized .020 for example, what is that based on? Is it .020 over standard factory bore, or .020 over what the damaged cylinder is measured to be just prior to boring? Just trying to understand the process so i don't feel so blind when handing over my power head. Do i need to provide std measurements to the machinist or should the marina already know? Thanks again

Re: 1986 90HP Evinrude VRO- my first rebuild project

Sorry for the repeated post earlier.... was using my smartphone to make the post and was apparently distracted

Does the crank or rods need to be polished before reassembly?? I have read that some prefer it, but the marinas made no mention of doing that before putting everything back together. Thanks again