90hp rude no power, extreme fuel consumption

[need 2 fish]

1987 evinrude 90 was rebuilt a year and a half ago and was running 5000 rpm at 35-40mph. a ring cracked after 10 trips & destroyed the block. Out of warranty so the mechanic made an effort to afforbaly find a good used block to replace. First run out with no gear we found the engine quieter and had difficulty getting the boat on plane. Second trip with normal fishing gear the problem got progressively worse and fuel consumption was phenominal, pulled plugs, oily but good, throttle linkage correct no water in fuel and proper oil/fuel mix. engine acted like the boat was full of water,took a block to get on top, engine will only turn 4200 rpm and run 27 mph (17 foot Sabre Tri Hull). Timing at 28 BTDC and all pugs seem to be firing. Could the mechanic be usingthe wrong carbs/jets? He says the engine is quieter due to it now having lower compressin heads. changed props and only turned 100 rpm more but no other performance improvements. We feel like we have a 40 hp on the back of the boat now but are burning fuel like a 225. Any suggestions will be appreciated, have not done a compression check yet but mechanic says it's fine.

 

[DJ]

Re: 90hp rude no power, extreme fuel consumption

need 2 fish,<br /><br />The best indication of engine health is compression. Do you know what yours is?

 

[need 2 fish]

Re: 90hp rude no power, extreme fuel consumption

Not yet, I'm taking the mechanics word right now that there all good but will verify myself soon.

 

[BKool68]

Re: 90hp rude no power, extreme fuel consumption

I would look to see if one of your floats is sticking open. Pull the cover of your silencer off and pump on the squeeze bulb. It should get hard and stop pumping. If you see gas coming out of the carb overflow that needle is not seating.

 

[Walker]

Re: 90hp rude no power, extreme fuel consumption

Test the check valves in the recirculation system.

 

[need 2 fish]

Re: 90hp rude no power, extreme fuel consumption

Doing a compression test tomorrow. Do all 4 plugs need to be removed when checking each cylinder? The mechanic said the knew to us block now has lower compression heads on it due to it being a newer model. What does this mean and what should the approximate compression be? Unless I'm mistaken, the proper method for the test is to spin the engine over, watch the needle peg three times, note the p.s.i. and hold for leakdown check. Am I missing anything? Also, How would I check the recirc system? You're not talking about venting are you?

 

[phatmanmike]

Re: 90hp rude no power, extreme fuel consumption

yes. remove ALL plugs, uless you want one of them starting and blowing you engine and guage to smithereens

 

[need 2 fish]

Re: 90hp rude no power, extreme fuel consumption

Sorry, I meant do I remove the plugs themselves all at once or individually or does it matter. I am aware that all plug wires must be removed to perform the test but thanks for the safety tip anyway.