Compression 110/105/90?

[huntxtrm]

Is that bad? It's a 74 Johnson 70hp. Piston tops look clean, by flashlight?

 

[boobie]

Re: Compression 110/105/90?

A little out of wrack but how does it run ?? You may just need a good de-carb.

 

[huntxtrm]

Re: Compression 110/105/90?

I'll try the decarb trick. But these are cold numbers. I got other problems, I think. No it does not run at the moment. Conked out on me last night. See my other thread on spark plug type? I think they are wrong

 

[boobie]

Re: Compression 110/105/90?

You can do the compression check hot or cold.

 

[huntxtrm]

Re: Compression 110/105/90?

Oh, I thought I read it had to be hot. I'll de carb as soon as I get it up and runnin. What can I use to de carb, does it have to be a special solvent?

 

[boobie]

Re: Compression 110/105/90?

I've always used BRP Engine Tuner but I'm sure others will chime in with other ideas.

 

[Anchor Marine Repair LLC]

Re: Compression 110/105/90?

Based on the idea you were looking for a problem (compression test), it's bad. On a 3 cylinder 70 Hp like that, I always see healthy ones 120 plus. Anyway you look at it, 90 is no where close to what the engineer designed it to run with.

Carbon build up doesn't cause a motor to just "conk out" and die. Unless it hooked a ring, which is fatal.

Don't waste too much time or any amount of money on it.

Pull the cylinder head or have a marine technician do a leakdown test on it to confirm the severity.

Leakdown Test Mercury - YouTube

 

[huntxtrm]

Re: Compression 110/105/90?

So compression is rings or reeds, most likely? Right? I'm not much on boat motors, but on other 2 strokes this seems fair. Unless, of coarse you fry a piston. And pistons not fried. Reeds are slammed shut, and look like new. So, it is most likely a ring, or gaulded cylinder wall. But the piston should fail, before a cylinder wall. I hope. My question is, if its rings, is a motor this old worth fixing? I'm on the fence, thinking about just buying a newer motor. But I've had a few of these older ones, and when they run right, they seem to be good motors. Sounds like your a mechanic, what is your opinion? I bet you've seen a few of these. Thanks

 

[huntxtrm]

Re: Compression 110/105/90?

Ok, I got it running! YEA! got a slight miss. Could that be the compression problem, causing that? Seems, I had the wrong plugs in it. Or, at least not very good ones. But back to the compression issue. Is this motor worth fixing? I can run it like this for a little while, I would think. Miss is not that bad. Cant figure out what, else it could be. I tore apart the carbs and cleaned them. They were already clean as a whistle. All jets and fuel holes flowing good. The carbs have no adjustment screws in them. Only jets, so I guess balancing the carbs is out of the question? I don't think my manual covers these carbs, I'll look. Any new advice would be appreciated. I have a video of the motor running. Is there a way to post a video on here? Thanks

 

[Anchor Marine Repair LLC]

Re: Compression 110/105/90?

I put my videos on YouTube, then put the link here. So that's what this Leakdown Test Mercury - YouTube is.

As far as if it's worth rebuilding, it's a personal judgement. To have it done professionally, you'll have $1800 + into it. But finding a good used one is next to impossible, and you still have the question mark of the reliability since it was used.

I'd rather rebuild my own motor (have it done with warranty in a repair shop) than spend any sort of money on a used motor gamble. It depends on how much you like boating, if you want reliability, cash available, etc.

 

[huntxtrm]

Re: Compression 110/105/90?

I put my videos on YouTube, then put the link here. So that's what this Leakdown Test Mercury - YouTube is.

As far as if it's worth rebuilding, it's a personal judgement. To have it done professionally, you'll have $1800 + into it. But finding a good used one is next to impossible, and you still have the question mark of the reliability since it was used.

I'd rather rebuild my own motor (have it done with warranty in a repair shop) than spend any sort of money on a used motor gamble. It depends on how much you like boating, if you want reliability, cash available, etc.

Really good video! and info! I'm gonna try that on this old motor. how did you convert to the spark plug thread size? to the quick connect on the air hose? Or are Spark plugs a standard size? Like on a quick connect?

 

[huntxtrm]

Re: Compression 110/105/90?

Oh, and I really like fishing out of a boat,. But, trying to do this cheap as possible. But, time is money, so if it weighs out, I might be just getting another motor. Are parts hard to find for these? As far as rebuild parts? Rings, bearings, etcc.... might be a winter project for me. Plus a learning experience, to boot.

 

[Anchor Marine Repair LLC]

Re: Compression 110/105/90?

Really good video! and info! I'm gonna try that on this old motor. how did you convert to the spark plug thread size? to the quick connect on the air hose? Or are Spark plugs a standard size? Like on a quick connect?

That's a leak down tester. It's a special tool, but very standard for us 2 stroke guys. For what they cost new, there's no advantage to making your own. You can get them delivered for under $80. It pays for itself the first time you use it.
SNAP CYLINDER LEAK DOWN LEAKAGE TESTER EEPV309A | eBay

 

[Bosunsmate]

Re: Compression 110/105/90?

check your sparking to look for the cause of the miss.
Once thats sorted then-
Do a decarbon and if it has all the power needed, then if it was me id keep it and put the money into a electric fishing reel.

 

[huntxtrm]

Re: Compression 110/105/90?

That's a leak down tester. It's a special tool, but very standard for us 2 stroke guys. For what they cost new, there's no advantage to making your own. You can get them delivered for under $80. It pays for itself the first time you use it.
SNAP CYLINDER LEAK DOWN LEAKAGE TESTER EEPV309A | eBay

Ok, I'll look into buying one. It looked homemade to me, that's why I was asking. Thanks

 

[huntxtrm]

Re: Compression 110/105/90?

Motor Running - YouTube Heres a link to it running. It seems to be missing, you tell me. Maybe I worry to much! Ive been known to. LOL

 

[Bosunsmate]

Re: Compression 110/105/90?

Sounds A-ok.
Buy some seafoam-decarb it and go for a fish.
Whats the camo paint job for? You planning on doing some bootlegging?

 

[huntxtrm]

Re: Compression 110/105/90?

if you notice, it has water running out from between the lower unit and the exaust housing, and up by the hinge? is that normal? or is there a gasket or something wrong, or missing? I know I need a seal on my shifter, I keep getting water in my lower unit oil. and there is no oil leaking from my lower unit, at the prop. So, I assume its the shift rod seal? Next project if, this motor turns out worth while.

 

[huntxtrm]

Re: Compression 110/105/90?

Sounds A-ok.
Buy some seafoam-decarb it and go for a fish.
Whats the camo paint job for? You planning on doing some bootlegging?

Ducks, FEAR ME! Well actually they laugh at me.

 

[huntxtrm]

Re: Compression 110/105/90?

Ok, took it out. No power. Used to run 38mph, now runs 21mph. Buddy told me, it's because my gas is a month old? Is fuel really that bad? It idled smooth, just no power. I didn't get jets in the wrong place, did I? Smallest jet goes in the bottom of the carb, and larger one goes behind, where normally would be a mixture screw. Correct? Just a thought?