115 & 150 evinrude compression issues

[pistnbroke]

I think its just the foam and the extra oil ..run these older motors at 50:1 ... you did well to get the comp up ..if you suspect seals on the crank between cylinders as being worn you can put seal expanding liquid in the oil and that will expand them 4 % ( I soaked an old lip seal in it at 21mm and after 3 weeks it was 19mm and supple ) great work ..now give every one who helped you some rep ..I see yours has gone from 10 to 13 so somebody loves you ...ha ha

[bigdawg10132009]

absolutely pistn!!! thanks EVERYBODY for all of the helpful advice.....i feel mo betta about spendin' the $350.00 for the boat, motor and trailer now....the motor is a VRO....do i need to change the VRO fuel pump out to a standard pump of just plug the oil line off and let her run....there looked like there was smoke coming from the fuel pump for some reason......

[pistnbroke]

VRO I assume you mean its oil injected ....so if you want to run on pre mix you just disconnet the pump and pipework and put 50 to 1 in the tank only .....if you do that and dont forget the oil ...Must be TWC 3 for outboards not chain saw oil the you can be sure its getting lubed

fuel pump and oil pump ..often electric in the tank are two diffeent things .the fuel pump works off crankcase pressure pulses ..no leccy required

[bigdawg10132009]

yepper....oil injected......
got some of the stuff specific to rudes.....

[Frosty]

For those not in USA, what is seafoam?

Brake fluid softens carbon deposits.

[bigdawg10132009]

seafoam is a liquid decarb agent (seafoam is the brand name) that can be put in the engine cylinders directly and/or in the gas and it also comes in spray form that can be sprayed into the carbs while the engine is running to help decarb rings, pistons, carbs etc.....

[powerabout]

Originally Posted by pistnbroke

I think its just the foam and the extra oil ..run these older motors at 50:1 ... you did well to get the comp up ..if you suspect seals on the crank between cylinders as being worn you can put seal expanding liquid in the oil and that will expand them 4 % ( I soaked an old lip seal in it at 21mm and after 3 weeks it was 19mm and supple ) great work ..now give every one who helped you some rep ..I see yours has gone from 10 to 13 so somebody loves you ...ha ha

pistnbroke
the seal rings between the cylinders are metal all US OMC / MERCS.
You need to have a built up crank to be able to put a seal on the crank which some jap stuff has.

only rubber seals are top and bottom of the crank.

[pistnbroke]

I think you misunderstand ...between each crankcase chamber there is a seal and if this leaks the transfer to the combustion chameber is affected ...yes/no

[Frosty]

Youve never had an outboard apart have you Piston?

There are no seals, not like you are thinking. They are called labyrinth seals.

They are close tolerance ridges that will allow air to pass but so slow and so poorly aerodynamically they seal one cylinder from another.

But you knew that didnt you?

Or as on OMC they are like huge piston rings that fit on the crank.

[powerabout]

yep wot he said

most small engines have labyrinth and larger seal rings so all omc V4, V6, V8 and merc V6
I'll bet the same with Yam but never played with them.

[pistnbroke]

sorry mate the ones I have had apart have had lip seals between each crank chamber .the last two cylinder susuki had 3 seals two outer and one in the center .....the crankshaft can be taken apart in sections to replace them which is a big pressing job which is why I suggested the seal expansion oil

hey you are a bit Frosty aint you ...ha ha .....stay cool but not frosty !!!!

[OzarkBoater]

I have a buddy that is looking at buying a 18' Hydra-Sports 175 with a 150hp Evinrude motor.

He had a local dealer mechanic check it out and they reported that the bottom cylinder in each bank had compressions of 90 and the rest of the cylinders were reading 100. They didn't give him any guidance as to how serious this was and explained that an overhaul would run around $3500.

If the boat starts, idles and runs out smooth, how concerned should he be?

The boat is very clean, possibly too clean, and we aren't getting any other red flags from the owner.

The asking price is around $6k. I'm just trying to give my friend good advice.

I'm just a shade tree mechanic and don't have much experience with outboard motors. Over the years, I've always had good luck with just doing an extensive test driving and looking for problems. I don't want to steer him wrong, but at this point, I'm recommending to go ahead any buy it.

Any advice on this would be very helpful. Thank you for your time.

Mike

[pistnbroke]

A variation of 10 psi is not serious but you should remember that any sediment and **** is likley to fall to the bottom of the block and cause water circulation problems on the bottom two cylinders so this is no doubt the start of the end or an indication that work will be required in the future. again it depends on price and how many hours per year he is goning to put on it and how difficult it would be to clean out those water passages.

[OzarkBoater]

Originally Posted by pistnbroke

A variation of 10 psi is not serious but you should remember that any sediment and **** is likley to fall to the bottom of the block and cause water circulation problems on the bottom two cylinders so this is no doubt the start of the end or an indication that work will be required in the future. again it depends on price and how many hours per year he is goning to put on it and how difficult it would be to clean out those water passages.

Thanks much pistnbroke for your advice on this...

My friend bought the boat last night. It ran great, though it appears to be over propped for top end with a 4 blade staleness 22 pitch. So it doesn't have much hole shot at all. It also has lots of torque steer when attempting to turn left if it is trimmed all the way down, but much less as you trim it out. I'm guessing that is normal. Let me know if it's not, and/or what you recommend.

I suggested he try a 19 or 20 pitch 3 blade staneless for the best of both hole shot and top end.

The boat ran out at about 55 mph with 3 fat boys in it.

Any prop feedback would be greatly appreciated.

Now, when we popped off the motor cover the mechanic who checked out the engine wrote the compressions on each cylinder head. It turns out the two lower compression cylinders (reading 90) were not the bottom ones in each bank, but rather the bottom 2 in the left "port side" bank (Left middle & bottom on the left bank of the v6. All others were at 100).

Does that change anything about our prior discussion?

Should my buddy next run some Evenrude engine reconditioned through the boat, which I assume is their brand of seafoam type cleaner?

Thanks again for your rapid response yesterday. Let me know your thoughts at your convenience.

Mike

[pistnbroke]

I dont consider 10 psi serious but if you can clean out the water chanels its a good idea on an older engine..
\
For the prop you can make no decision until you know the rpm at full throttle with your 3 fat mates on board ....check the rpm against the makers rev range permitted and if its too low as you suspect then taking 2 in off the pitch will raise the rpm by 400 .....if the 4 blader is too much it would be better to do a test with a borrowed 3 blade ali or stainless before you buy one as they do say a 4 blader is equivalent to adding 2 inches of pitch ie a 22 pitch 3 blade may be fine ......without a rev counter you can tell nothing.