motor shaking

took my boat out the other day and the motor started knocking and shaking really bad when i put it in gear. doesn't do it in nuetral...only when it is in gear or reving it up. any ideas?

[fredhatch]

Have you struck the lower end on anything? Is there more smoke than usual? Sounds like a foul in the plugs, maybe a fuel problem, or you have bent something.

havent struck anything..just started acting up a little bit on the way back to the launch one day and the next time i took it out it was alot worse. checked the plugs and they are ok

[jeffman]

MIKE,

How old are the plug wires? You could have a broken sheathing on one of the plug wires allowing it to fire across and shorting out. The other possibility (HORRORS) is that you have a hole in a piston dome. I think you need to get it to a mechanic before you run it again.

JackL

[jglassguy]

How big a motor, does it have coil packs on it?

the motor is an evinrude 40 hp. someone told me that it may be a bad bearing in the lower unit. was supposed to bring me parts saturday since he worked at a marina but never did. sucks that i have a tourney tommorrow and no thing but a trolling motor right now

[crhye250r]

Definately need to check that out further. My first inclination is that either you have something severely out of adjustment in your shift linkage. (although it doesn't make the noise in neutral, it may not be going into forward all the way). Or you have an issue in the gear case, which is never a good thing. I would reccomend taking it to a reputable mechanic and having them do a compression check to rule out any piston damage, and run the boat in the water. If the boat ever sets for a length of time with no use, a dirty carb could make an engine miss severly. A good mechanic should be able to diagnose it fairly easily.

GOt a Yamaha 40 that does that very same thing when low on oil. Give it a try!

K

[bass kicker]

bad bearing on the connecting rod or worn piston rings eiter thin is bad

[jigicant]

found out it mwas the forward gear...teeth were just about completely worn off. also had a few other things wrong..looks like a new lower unit will be put on it this spring

[bassintom]

on a 40 h.p. the lower unit is a simple disassemble and rebuild.i've done them on my kitchen table in less than an hour.if you're going that far,make sure you replace the water pump.they aren't expensive and it'll save you trouble down the road.
just make sure you put all the thrust washers back where they belong

[1FASTLASER]

Jigicant
Like Bassintom said that small a engine is VERY simple for the mechanically inclined. A clean working surface and some patience is all you need. Parts can be had fairly inexpensivley for that motor and save you a ton of money doing it yourself. Dont need any special tools to do it neither being that the lower hasnt been neglected. If you need any help give me a holler as I have just about every manual ou there if you need any specifics.

[jigicant]

thanks laser... am going to replace water pump while its apart and the pump housing is also cracked so i have a few things to replace.

[zooker]

my lil yammy shakes while idlin but not a problem above 500 rpm.
lower units are very simple to rebuild. good idea in replacing the water pump impeller. you also want to check the water inlets and water race ways inside the lower remove all debris. laser elouded to it some were else that muddy water has grit in it. if you fish muddy water alot it will build up grit in the race ways and chew the empeller up.

ah notice your location as michigan.
one thing i do every time i pull the boat out of the water in the colder temps-any time the air temps are below 32 degrees- is i dry crank the moter let it fire and shut it off. this rids the race ways of water and the water in the pump housing. even new moters DO NOT drain this area. water freezing in the pump housing and race ways are the #1 cause of lower unit cracking.


zooker

[bassintom]

make sure there is some water in your motor before you crank it over.a dry impeller can go south in a heartbeat.

[1FASTLASER]

What year 40hp is it jigi?? I would suggest the use of synthetic oil in the lower aftetr rebuilding. The qualities of the synthetic are a big plus. Yes they are a bit pricey but the advantages outweight the disadvantages in my opinion.
Bassintom
Yes a impellar can go quite quickly if you fire the motor when it is Dry. But remember it just came out of water. Water is tstill in the motor therefore for the few seconds that you spin and fire the motor it is still lubed. NEVER EVER dry fire a motor that has been sitting in the back yard or garage because as you stated the impellar can and will eventually go south. The big plus when firing the motor when its cold after putting it on the trailer helps tremendously to keep from cracking a lower due to freezing temps. I've been doing this for years and never had a problem. I might also add that I change impellars very year as part of my annual maintenace program. Water is one of the "bloods" needed to keep a motor alive therefore I take no chances when it comes to that.Plugs,impellar,fluid checks and changes,bolt tightening and a good dose of Sea Foam every year and the outboard will give you relatively very little problem.