40+ Crankcase gets very hot!

[John1952]

Thanks for your input Ted, I didn't give that a thought I will take the prop off and give it a run in the bin and see how she fairs

[Waggles]

OK John,

On saturday I went out to my mooring using the trusty 40+, It was quite a warm day and I deliberately gave it some welly. My crankcase was what I would describe as 'very warm', I could certainly keep my hand on it for any length of time, comparing it to water baths we used to have in the labs I would estimate it around 60 degrees C. I ran it again in the yacht club bin to flush it after with much the same result. Not surprisingly the barrel was a similar temp. The head was f*&^%$g hot.

I did notice that once the motor has stopped things get a little hotter presumably as the exhaust temp redistributes itself and there is no cooling water.

Note that my motor does pump water very well, even in the tub.

[John1952]

Hi Waggles,
just reading you post again and am not sure if you could, or couldn't keep your hand on the crank-case!
I went out on the boat yesterday and fired up the 40+, ran her for a good half hour under load and she was, as you say, f*^%&*g hot, fingers on and off pretty pretty sharp I can tell you!

[Waggles]

Hi John,

I COULD keep my hand on the crankcase for as long as I liked, only the head was v hot, barrel was ok to touch too. Admittedly I didn't run for 30 mins, it was about 15 ( to the mooring and back with a v short break on the boat ) but I don't think it was getting any hotter.

Yours does sound like it is running a bit too hot and can only think ( as has been previously suggested ) it is the main bearing. If you are sure it is being lubricated correctly ( ie oily gunk in evidence having leaked through it ) then I am afraid a bent crank is likely.

[Todd]

John,

If water flow is good, the other easy check would be the spark plug color. Give it another good hard run for half an hour, shut it down abruptly and ckeck the plug. A color lighter than a medium tan might indicate a lean mixture which will cause hot running. Assuming the carb is scrupulously clean, you could then back the slide's jet needle screw out a half turn and see if things improve at all.

Todd

[John1952]

Hi John,

I COULD keep my hand on the crankcase for as long as I liked, only the head was v hot, barrel was ok to touch too. Admittedly I didn't run for 30 mins, it was about 15 ( to the mooring and back with a v short break on the boat ) but I don't think it was getting any hotter.

Yours does sound like it is running a bit too hot and can only think ( as has been previously suggested ) it is the main bearing. If you are sure it is being lubricated correctly ( ie oily gunk in evidence having leaked through it ) then I am afraid a bent crank is likely.

Thanks again waggles, are the main bearings the same size in all the Seagulls?

[John1952]

John,

If water flow is good, the other easy check would be the spark plug color. Give it another good hard run for half an hour, shut it down abruptly and ckeck the plug. A color lighter than a medium tan might indicate a lean mixture which will cause hot running. Assuming the carb is scrupulously clean, you could then back the slide's jet needle screw out a half turn and see if things improve at all.

Todd

Thanks Todd, the colour of the plug seemed ok!
I did however screw the jet out half a turn as you suggested, and she started a lot easier than before but unfortunately it was still f*&)%^g hot

[Waggles]

Hi John,

I notice the part numbers for the main bearing bushes are the same for both the forty and century series so this implies they are the same, however there are differences on the older engines which is why they should not be run on 25:1

If new bushes were fitted they should be line reamed, just wondering if you may have a 'bitza' where the crankcase halves from two different motors have been mated together ( perhaps to replace a crankcase half where the tiller mounting has broken off? a common thing to happen ) in which case even though the crank may not be bent the bushes may be slightly out of line. If this is the case as both bushes will have been worn for a while line reaming now MAY not work as you may introduce play in the bearings in order to line things up.

Personally, as 40's are thankfully fairly common I would give John a call and see what he has in the line of 40 bottom ends ( you could gamble on e-bay but ...... ) or alternately think of new bushes suitably reamed?

Would suggest a strip of the bottom end this winter to see what you can find out before proceeding, you may still find just a dry bearing!

[John1952]

At Long last hopefully, the problem is solved
After a complete strip down, no tight bearings, no bent crank, however, after taking the head off the waterways were quite blocked!
Just goes to show, that even though there was, what I thought, a good water-flow the engine obviously wasn't getting enough water to keep it cool enough It now gets hot but not too hot to touch
Just like to say thanks to everyone for their help and advice a good learning curve for me!

[atoyot]

...Just goes to show, that even though there was, what I thought, a good water-flow the engine obviously wasn't getting enough water to keep it cool enough..

Good job on this, if I may say so. And yes, just as with automobiles, seeing water circulate tells us little about the ability of the cooling system to carry off heat. If others are so unfortunate as to run into the same problem, begin the tear-down with the cylinder head and that might be as far as one has to go.

Glad to hear of the success.


- Ted

[Waggles]

Thanks for letting us know John it helps a lot to get the resolutions to problems posted as others can then search them.

Guess your water was taking a short cut! just goes to show how easily you can be misled even on a motor as simple as a Gull! I have everything crossed this is the end of your problems.