lumpy in gear

[titch]

hello to all. I have a 1990 evinrude 90hp V4 that is running a little rough at idle but when i put it into gear it becomes very lumpy and does so at all revs. its that lumpy it vibrates the boat. I have changed the plugs and leads and checked the spark and seems OK, cleaned the carbs, checked for leaks. timed the engine. now i am at a loss. can a head gasket cause this problem although there are no water leaks. Any help will be appreciated.

 

[tashasdaddy]

Re: lumpy in gear

have you check spark after the motor has heated up. lumpy can means many things, i think of pillow, or mattress. have you pulled individual spark wires while the motor is running, to see if that cylinder is running.

 

[bustermin]

Re: lumpy in gear

please give a little history, has the motor been sitting? was it running good then started doing this? did it overheat, what makes you jump straight to head gasket? has anybody changed anything (i.e. any recent repairs). try pulling spark plug wires one at a time when its running to see if you have a dead cylinder.

 

[titch]

Re: lumpy in gear

hi thanks for your replies. have checked all plugs while running warm and cold and the sparks are strong on all.

History. the boat has been used approx 4 times a month for the last 2 months but before was sitting still for 3 months, fuel was treated for this and have re fueled since then. Started the engine with a little trouble 2 days ago and it run away to 6000 rpm and clunked into gear shocked me, first time this happened. (thats why head gasket come into mind) checked why and the bottom carb linkage had moved so one was clossed and the other was 1/4 open. rectified this and the trouble has been from there really. checked sparks, renewed plugs and leads, cleaned carbs, checked for leaks. For the age of the engine the motor was working ok untill then.

 

[titch]

Re: lumpy in gear

sorry lumpy, it shudders/vibrates alot, so much you can feel it through the boat. although still get max revs out of it but uncomfortable. When you go from slow and open the throttle up it holds back a little and splutters then shoots off. when in nuetral the revs are good all through with little vibration. sorry but trying to give as much info as i can.

 

[clemsonfor]

Re: lumpy in gear

check the compression, maybe a cracked ring. On the one cyl it could have extra wear from where it ran away at full throttle, the on cyl that was only a quarter open did not get adequate lubrication b/c it wasent getting enough fuel in the cyl for the rpms it was going.

Could not really tell from your post but it sounds like it could have been slammed in gear at 6000 rpms which could have broken part of the gears off so there is now a bad spot that clunks everytime it goes around which would get worse the fater you go. I suspect this is the problem if it indeed was slammed into gear at 6000 rpm's. pull the oil in the lower unit and look for lots of metal shavings to chunks of gears.

 

[titch]

Re: lumpy in gear

Thanks for your advice and will check the compression when i get a tester. the gear problem i will check but i might of missled on one of the posts as i dont think it gets worse with speed infact at top end it eases out a little.

 

[titch]

Re: lumpy in gear

checked compression and 1/2/3 are at 10.5 barr and 4 is at 10 barr. that is a drop of about 7 psi when converted the book says more than 5 then there is a problem but 7 doesnt seem to be too harsh to cause the problem or am i incorrect on my thinking. I have noticed a rattling sound that was there before but no were near as noticeable than it is now, it is coming from the center to rear area of the engine i think. Put the pistons to the top of there motion to check if there was any play in the pistons but does not seem to be. Checked the oil and no metal bits have been found (thank god) has anyone got an idea what the cause could be?

 

[freddyray21]

Re: lumpy in gear

my thoughts lean to the carb linkage not being synched given that you said you experienced a linkage problem. both need to be the same or the cylinders will be getting different amounts of fuel and it will vibrate like it's not firing right. recheck the carb linkage.

 

[bustermin]

Re: lumpy in gear

if i remember correctly, 10 bar is approx. 150psi which should be good. i would double check carb adjustments. but the rattleing that is getting worse should be addressed even if it has nothing to do with your current problem, you dont want to ignore somthing that might be an easy fix and let it turn into a major problem.

 

[titch]

Re: lumpy in gear

i have checked the linkages and they are as the book says and that is make sure they are both closed which they are. it does sounds like its misfireing but all sparks are good. totally baffled now.

 

[clemsonfor]

Re: lumpy in gear

i hope you noise is not rod bearings!!

 

[titch]

Re: lumpy in gear

why do you say hope its not rod bearings is this bad?