engine miss under load

zindale · Mar 24, 2005

howdy all thanx in advance for any help. i have a 1989 force 150, on a 19 ft fish/ski boat the problem im having has been since i bought it last year. it misses under a load in water through all rpm ranges, enough that it shakes whole boat. inspected clutch dog npf.shop says it needs overhauled. $$$ twice what i payed for it. i tryed pulling one plug wire at a time and grounding, driving and miss still there not changed. if i killed the cylinder that was missing wouldnt it stop missing intermitantly. i think its an electrical prob. any help thanx

rosco_59 · Mar 24, 2005

Re: engine miss under load

When you ground the wire you pull if it is not the one that is bad then it should miss more if that plug is firing. When The one that is not firing is pulled there should be no differance.<br />Pull all the plugs and see what they look like. You might be able to see which one is not working from the look of the plug. You need to find out which one is not working before you can fix it.

eurolarva · Mar 24, 2005

Re: engine miss under load

YOu may have a spun prop. An easy test would be to use a permanant marker and draw a line on the prop to the prop nut. If the prop is slipping it may give the impression of a miss. As the prop slips the RPMs will increase. If the prop is slipping the line you drew will not line up.

Docdoc · Mar 24, 2005

Re: engine miss under load

When you pull those plugs, hook them up to their respective wires and gournt the base of each plug to the engine and crank briefly one at a time. Do this in a dark place or at dusk and note if any of them do not fire. You may have a broken wire, or a bad coil.

zindale · Mar 24, 2005

Re: engine miss under load

have indexed prop and not spun.shop says comp. is 170 on all but cyl 3 only 100. if cylinder is low will miss all the time not just erractly. 100 is low but not totaly dead. i am an auto tech. just a little intimidated by outboard is my first boat.

zindale · Mar 25, 2005

Re: engine miss under load

took boat out again and it seems like you trn key off then on could this be the cdi module?

rosco_59 · Mar 25, 2005

Re: engine miss under load

I think I might look at the trigger and check to see if it has a problem. If it seams like you turn the key off then on again it would be before the cdi, I would believe. Check the wires coming from stator to see if one is shorting out on something. Check all of your ohms reading that you can. That might give you an indication.

zindale · Mar 25, 2005

Re: engine miss under load

thanx will try tomorrow, the shop called said they had a trade in 89 mer 150 4 sale installed for 1900.00, would i be better of with this merc or keep fighting the force?

rosco_59 · Mar 25, 2005

Re: engine miss under load

zindale, that would be your decision to trade, I think if I fought it that long with no help I would be tempted to trade myself. But I would be afraid that it could be something small and cheap to fix and I would have spent all the money for nothing. I would have a hard time making that decision. Good Luck

eurolarva · Mar 25, 2005

Re: engine miss under load

When you make that decision keep in mind the cylinder with the low compression. If it is just the head gasket it is a cheap fix. If the cylinder or the piston is damaged the merc sounds like a better option.

Docdoc · Mar 25, 2005

Re: engine miss under load

Eurolarva is right. That much difference in compression is not good. I'd get the compression numbers on the merc before I bought someone else's problem though.

zindale · Mar 27, 2005

Re: engine miss under load

will go get boat tommorow shop only wants to rebuild or replace, wont miss out of water shop wont take to water says he knows whats wrong with out that. will try to repair myself. wish me luck

golor · Mar 28, 2005

Re: engine miss under load

well since u have had compression checked and low compression i would take the head off and replace the gasket may fix it u can pick up a head gasket for $40 bucks

chuckz · Mar 28, 2005

Re: engine miss under load

Since you don't know the history of this engine, the first thing I would do is a decarb. It is possible and even likely that it would fix your compression and missing problem. See the FAQ's forum for the procedure.

zindale · Mar 30, 2005

Re: engine miss under load

thanx for help will try decarb hopefully this weekend. been raining alot latley. really not ready to spend that much money yet is almost twice what i gave for boat.will keep posted. thanx again

zindale · Apr 2, 2005

Re: engine miss under load

did the decarb didnt help removed head found #3 cyl piston has dent in top from ring toward top of piston. # 4 same way except piston beat all up.looks sort of like melted. gonna attemp to overhaul myself. any suggestions to were to purchase. pistons and gaskets.<br /> any idea what could have came apart and tore pistons up?

chuckz · Apr 4, 2005

Re: engine miss under load

We'll decarb was worth a shot.<br /><br />Since a set of cylinders are damaged, I doubt it was something coming loose. My guess is that the mixture feeding those two cylinders was too lean. Some photos of the damage would probably help some of the more experienced guys give you an accurate diagnosis.

zindale · Apr 5, 2005

Re: engine miss under load

dissasembled powerhead found broke rings on cyl 3 and 4 gonna o-haul havin trouble finding machine shop to bore block. also is there anywhere on the net to order a complete o-haul kit including pistons and all thanx

eurolarva · Apr 5, 2005

Re: engine miss under load

Post your model number. That will help finding the parts you need

zindale · Apr 6, 2005

Re: engine miss under load

well having trouble paper tag on motor unreadable have a couple numbers off of block casting numbers i guess B41293, M618919, only numbers i can find.

engine miss under load

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