Any inherent problems with

[mphy98]

Are there any inherent problems with a 90 90hp rude or johnson motors that I should be aware of? The new to me fishing boat looks to have this motor. I have narrowed it down to 2 and one has a rude, the other a johnson. I believe they are made by the same mfg company. thanks in advance, bob

Also are these oil injected? forgot to ask the dealers

 

[jonesg]

Re: Any inherent problems with

No inherrent problems.

But you'd want to see compression numbers and test gear oil, a mechanic will give it a going over for a fee.
Better to take a test ride when possible.

 

[5150abf]

Re: Any inherent problems with

You are correct, OMC made both of those engines, if they are the same year the only difference may be the stickers and the color.

That is a really good year for them, before they started throwing alot of plastic on them.

As jones said, always a good idea to get them checked out by a pro, if they are at a dealer ask to hear them run at least and get compression numbers on them, If you can run the boats that is always best.

They were oil injected new but alot of guys disconnected it so definately ask.

If they were taken care of they are really good engines, anything from the early 80s up OMC are really good bullit proof engines.

I have an '81 Evinrude 50 with the original power head and 135 compression so if you take care of them they will last a very long time.

As a point I remember hearing that the 90s ran a lower compression so you would want 90ish or above and all cylinders within 10%.

 

[MichaelP]

Re: Any inherent problems with

This is good to hear as I just got the same motor 1990 Rude 90. Been soaked in salt water so this winter I'm doing a couple of things to it. Cleaning carbs, thermostat kit, fuel filter, Gear oil and fresh stickers and paint. PO changed the impeller last summer. Any other preventative actions I should be considering? My cold compression range is 112-123.

 

[emdsapmgr]

Re: Any inherent problems with

Compression issues start to be a concern when the readings on each cylinder are more than 10% different from each other. In your case, you are right at that edge. I am suprised that you'd see 123 with stock heads. Are both the heads on the engine similar in part number, or do you have a replacement head? 326504/505 are the stock head part numbers. I'd be looking inside the spark plug hole with a small penlight and see what is up. Maybe even pull the head is you can't see inside. It is typical if the compression numbers vary slightly from one head to the other (due to original factory manufacturing)

 

[5150abf]

Re: Any inherent problems with

MichealP, if you have never done a decarb or it has been awhile try that, then run it for awhile and recheck compression.

 

[MichaelP]

Re: Any inherent problems with

Thanks gents..I'll put a cab kit in her while I'm at it. I checked the comp before buying it with one of those cheapo rubber tipped guages that you just push on so I don't think my readings are very accurate. I'll check on the heads and get back to you.
By recarb you must mean carb kit right? I just ordered 2 carb kits and 1 thermostat kit from iboats. Hope they are the right ones. Best prices on these 2 items so far and I looked around allot!

Thermostat Kit for Johnson/Evinrude, GLM 13270 - Sierra p/n 18-3673
(2) Mallory Carb Kit 9-37100 Part # 9-37100

 

[5150abf]

Re: Any inherent problems with

No to decarb you run a mix of Sea Foam and gas through the engine, it cleans out all the carbon build up in the engine and usually makes them run better.

I think it is a gallon of gas and a can of Sea Foam that you mix with oil of coarse, get the engine hot then run the foma through it till the engine runs bad, let it set with the engine off for @5 minutes then run it with your normal gas, run it hard if possible.

A warning, it smokes REALLY bad so maybe watch where you do it, the smoke is the carbon being burnt off so don't worry about it.

 

[MichaelP]

Re: Any inherent problems with

5150, 10-4 on the sea foam. When I got it in October I had it professionally looked over and winterized. I was told it needs to have the carbs cleaned. I decided that if I have to pull them off I might as well rebuild them while I'm at it.

The heads are stock. Looks like nothing has ever been done to the power head.