88 110hp V4 problems

[andy6374]

History here...This is a friends boat. I took a look for the first time last night.

Engine was surging a higher speeds and would always stall when put into gear. Then finally wouldn't run at all...he had lost spark. So he pulled the boat and...

Replaced:
Stator
Powerpack
Rect/Reg.
Rebuilt Carbs
New fuel pump/lines/tank...


He spark on all 4 now.

Now the engine runs again, but still doesn't like to go into gear without stalling and still surges (and sometimes boggs down but then sometimes comes back up to higher RPMs) at higher RPMs.

Now the plugs keep fouling. The cylinder heads are ice cold even after running at 1500 RPMs for 20-30 minutes in the water. So I told him that I thought that either the tstats are stuck open or there are no tstats at all. And that this would definitely cause a poor idle, fouling plugs and that the fouling plugs could definitely cause the surging. What do you guys think?


Also we did a compression test (on a very cold motor) and the results were
115,120.115,95. The 95 number isn't great and told him that this COULD be the problem but I told him to decarb and see if the numbers improve. Because if this thing has been running cold for a while I am sure that is a ton of carbon buildup possibly contributing to low compression in that cylinder (ie stuck rings).


Comments, suggestions?

 

[andy6374]

Re: 88 110hp V4 problems

bump

 

[emdsapmgr]

Re: 88 110hp V4 problems

The only ignition parts you have not replaced is the timer base and coils. Suggest you do a some tests on the timer base and compare with the manual specifications. The timer should output .3 volts cranking and 1.0 volts when running. You will need a peak-reading voltmeter for this test. Also 40 Ohms plus or minus 10. I like to put a timing light on each plug wire when under load and check the flashes. (strong/weak/intermittent.) If you find any weak spark, swap the offending coil and see what happens. Run the engine without the cowl-in a dark area, just in case one of the plug wires is shorting to the cowl latches. Weak/poor ignition can cause the stalling and surging you mention. Also low idle speed-should be 650 rpm in gear. You are on track with the cold running issue. I'd have a look in the thermostat housing and probably replace the stats and make sure the pressure relief valves are operational. A decarb on the engine is also a good idea on an annual basis, esp if it has been running cold. The rect/reg should not be part of your ignition problem.