90 Evinrude overheat

[geedo2]

Need a good tech for this one:
Working on a 1990 90 Evinrude which was rebuilt by a local shop after VRO failure. Tech had installed .030 pistons and circumvented VRO, recommending Amsoil premix 100:1. Guy that bought the rebuilt motor from the shop had it installed by the tech on his boat.....but later had it back several times because of poor running and bad idle. Guy says that he was never satisfied with the way it ran. Note: I see all new electronics from CDI. Guy.......we will call him Joe "boat owner", and Jeff the "tech" finally parted ways. So now Joe finds me 3 years later..........Joe never ran boat much at all........and has me fix the problem. Electronics checked out brilliantly so I checked fuel and filter.....all spotless. Noticed melting at base of power pack........obvious overheating.......even coil bases melted......wow!.......No overheat cut out or buzzer? Apparently not. Joe says always saw water stream. So next I check compression.......50, 90, 85, 90.......yuck! I suspect head gasket because motor had pretty loose head bolts with no dressing on threads or bolt head shoulders. Sure enough, cyl 1 blown into water jacket.......long time running that way with water pitting on top of #1 piston. NO scoring, all cylinder finishes flawless. Top of cylinders slightly blued and straw colored from heat. Very excessive piston clearance........can put a .022 feeler gauge between top of pistons and cylinder walls.
Here is my take: Jeff set up with too much clearance to begin with and then improperly torqued heads. Head gasket began leaking compression into water jacket and disrupted flow of fresh cooling water, "not salt water". As leak got worse, engine began overheating but still showed water out the indicator port. The excessive piston clearance and Amsoil protected engine from major meltdown..........
Okay, questions, whose fault is it and what can we do to fix the motor? At that clearance with overheated rings and 90 psi will this be a serviceable engine? Joe has $3,000 invested in this engine and wonders if he wants me to rebuild it for another $1,000........or try some head gaskets for $200. No comment yet from Jeff. This doesn't include hooking up the overheat protection / warning........Okay, Thanks for your help in advance, Geedo

 

[jakedaawg]

After three years there are no warranties I am guessing. Hes already got way more money in it than its worth. Make a nice mailbox out of it for him and sell him an E-tec.

 

[Chris1956]

Gee, 3 of the cylinders are close in compression. Are you sure the gauge is accurate? it is likely reliable. I would think a larger oversize piston on the low cylinder could fix it up, if the head-to-cylinder surface will seal.

I would recommend running a 50::1 premix using a TCW-III rated oil, instead of that snake oil.

 

[racerone]

Running 100:1 in a motor like that is a big MISTAKE.

 

[geedo2]

I agree with the ratio mix, but what I'm asking is what do you think about correcting the immediate problem with head gasket replacement? Then, what are the odds that this engine can perform adequately with that much piston clearance plus 90 psi per cyl, then consider how hot the rings got with the water flow problem? Lastly why didn't the engine warn Joe that it was overheating?

 

[geedo2]

Hey, techs......still no help for me? I hate to go back to marineengine.forum for an answer, but Mr Reeves is one dam sharp guy.

 

[Chinewalker]

Do the overheat sensors work? Easy enough to test the horn, anyway (ground the wires to the block with the ignition on).

Certainly won't hurt to try a head gasket and see if it runs. Nothing to lose at this point.

 

[geedo2]

Thanks and no alarm. Gaskets and center cover will cost him $200 so he would be out that much more cash for this experiment. I figured someone here could make an educated guess how this motor would perform/last with 90psi and that much cyl/piston clearance with heat damaged rings. I told the guy he will possibly not have a reliable motor, especially out on Lake Superior, it is a bit of a gamble. Lake Superior can hurt you.......and an engine failure is certainly a problem when fishing way offshore for trout and salmon.

 

[emdsapmgr]

A strong telltale indicates that it is pumping water up to the block. It does not indicate that it is circulating through the block and back down the midsection. If both stats are stuck shut you will get and instant overheat and a hot horn. Other overheat issues: you can overheat one cyl if the rubber water diverters were installed out of place during the overhaul. When this happens you can get an overheat and maybe no hot horn. Would be interesting to see what the carb main jets look like when they are held up to a light for a visual inspection.. If the oval hole in the valve body of the thermostat housing is plugged, the engine will overheat, too. Must be checked during overhaul.

 

[geedo2]

I only took off the affected head and gasket blown between combustion chamber and water jacket, lower cylinder still had been sealing but ready to go soon also. The compression pushing into the water jacket disrupted water flow by pressurizing the cooling system with air instead of water. The diverters are in place and the jacket chambers look very very clean. Checked top carb main jets and no deposits. One must always suspect jet restriction with use of ethanol, this boat owner "Joe" said he uses only non-oxy fuel......In Minnesota, it has to have a sticker on the gas pump stating, "for use only in off road, collector vehicles, boats, small engines".