Re-Built 90HP Evinrude

[pagraham]

I just picked up a rebuilt 1989 90 HP evinrude a local rebuild shop. The shop disconnected the VRO and said mix it 50:1, 12 gallon break in between 2k & 4k rpm, after that, it's broke in. I ran the 12 gallons thru it over the last 2 days and had a few issues I want to run by the forum for advice.
1) when flushing the motor and standing bare foot in water in the driveway, I get a shock when I touch the motor housing, inspected every wire on the motor and checked the ignition switch as well, didn't notice anything.
2)Runs rough between 1400 and 2200 rpm, seems to serge at some point when you barely move the throttle. Runs quite well otherwise
3) today after running it, I pulled the cowling and there was a salt crust formed aroung the head gaskets.
4) Got 5200 rpm WOT trimmed up a bit @ 40 mph
17' 1978 Montauk

Any advice would be greatly appreciated, I will take it back to the shop soon so he can inspect my rigging job, so as not to void the warranty, thanks

 

[ezeke]

Re: Re-Built 90HP Evinrude

1. The likely source of the shock is from the spark plug wires being too close to the latches on the engine cover; See if you can route them so that they are as far from the cover as possible.

2. May be related to 1. Usually surge is caused by air leak in the fuel system; includes the gaskets on the carburetors.

3. It's difficult to keep paint on the area between the cylinder heads and the block because of differences in the rate of expansion and contraction, so you get corrosion unless you use some form of water displacing product or T-9 or something similar. The head bolts should have been retorqued after the break-in period.

3. Top WOT RPM desired is 5800 with your average load so that you don't lug the engine. Typically reducing the pitch of the prop will solve that unless raising the motor higher on the stern does it.

 

[pagraham]

Re: Re-Built 90HP Evinrude

ezeke,
you were right, it only shocked me when I tried to latch the port side cowling latch, also when it was latched. I finally spotted a nick where the bolt head had dammaged the plug wire.

I think the surge was caused by the fact that I had adjusted the spark advance screw giving it some slop, it surged at 1400 to 2200 rpm. I ran the screw back all the way in and that has stopped.

The motor was bored 20/1000, would you say it is still a 90 hp?

It's on a 1978 Montauk, has a 15x13.5 Michigan prop, turns 5500rpm wot, little over 38mph, how does that sound?

Thanks

 

[ezeke]

Re: Re-Built 90HP Evinrude

The setup sounds good, with very little slip. The convention is to express the propeller diameter first, so it's a 13.5 X 15.

Your gear ratio for the canned calculators is 2.0: http://go-fast.com/Prop_Slip_Calculator.htm

The pistons all weigh the same, regardless of the bore, so any difference is very negligible.