5.5hp Johonson Seahorse 1961 - Rated Compression

[Loper4]

Does anyone know where I can get the targeted compression pressure of this 1961 twin cylinder 5.5hp seahorse? I will conduct a compression check and am not sure of what the compression should be.
Thanks.

 

[Lion hunter]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

It would be in the manual. Just do the test and post the results here if you don't have one yet. Athough you don't want low compression the numbers are not near as important as having both cylinders within 10% of each other.

 

[JB]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

There is no psi target, Loper. Guages, technique and conditions vary too much from one test to another.

What you want to look for is both cylinders compressing within 10-15%.

Healthy rope start engines often compress 50-60psi.

 

[OptsyEagle]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

I have the same motor and my guage gives me a reading of about 85psi on both cylinders. It runs like a top.

 

[Loper4]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

Thanks for the input - getting good comrpession - ~80psi in both.

 

[62larkowner]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

i aqquired a 1969 9.5 evinrude ,pull start, replaced impeller , ran great in barrel
* good 15 minutes * started several times ( hit on first or second pull)
no problems, took it out to lake got bout 600 yards out and died, no clue what went wrong has good spark seems to be gettin fuel ,

would not restart brought it home asked a few ?s to a friend said try compression test

bout 58 on both cyilinders ( was told that was way to low)

was told posably blown head gasket?

took head off gasket seemed to be ok (

what else could i bee lookin at and is 58 ok on the compression???

did i wast my time taking head off?

 

[jbjennings]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

You really need to post your own thread so you can get some good help.
To answer your question, yes, you probably wasted your time on the head gasket. But it's one less thing to worry about. Second, you'd have a better chance of winning the lottery than your motor having exactly equal compression that low (58 is WAY low on that motor). Don't worry about the compression. Find out what is wrong with your motor. They don't suddenly stop running at wide open throttle very often because of compression unless a dirt dauber nest under the cowl broke loose and the sand cut the rings out.
Here's what I'd do:
Do a real spark test. (I'm guessing you did your initial test without an actual spark tester since that's what I once did and it drove me nuts figuring out I had spark problems). Use a $6 spark tester from autozone.
If it's getting good spark, it's not getting enough fuel or the spark isn't timed correctly. I doubt that the timing is the problem unless you hit a stump and sheared the flywheel key.
Next, clean the carbs. It's not that hard. Totally simple, actually. And that's coming from someone that has nightmares about being forced to rebuild a carburetor from a car!
If the problem persists, check to see if your fuel pump working by turning it over with the hose coming from the pump off the carb. Use a friend to turn the motor over and see if it pulses fuel out the hose while you catch it in a cup. Actually, try pumping the primer bulb and getting it restarted after you replace your head gasket with a NEW one. If it starts to die on you again, have the primer bulb in your hand and pump it and see if the motor picks back up. If so, it's probably your fuel pump. If the bulb is flat, your tank vent is clogged or closed.
Retorque the head bolts in the proper pattern with a torque wrench or your motor will get ruined. You might check for head flatness before reinstalling by putting it on a pane of glass and looking for gaps. If so, rub it in a figure 8 pattern on a pane of glass with 400 grit sandpaper on the glass.
I'll bet you can fix it.
Good luck,
JBJ

 

[jbjennings]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

Aw shucks,
I just reread your post and see that it's a 9.5. Try getting it recranked with the cover off, then go out and run it again with the cover off. If it runs fine, then put the cover back on and retry it. If it dies on you again and won't restart, then get prepared to find your exhaust leak and try to fix it. It's a common problem on those.
Later,
JBJ

 

[62larkowner]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

thanx jbj i'll try all that once i get the new headgasket and t-stat n t-stat cover ( i broke mine gettin it off)

all this came from advice from some one else about the compression being low, they said it was a blown headgasket,

so i will get the spark tester and try that also..


will keep ya'll updated on what happens

 

[jbjennings]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

In retrospect, you might check to see if something like a bad kill switch is grounding your motor out. I'm no longer thinking spark but something fuel related. If it were spark related, you probably wouldn't get ANY spark now, since it's unlikely that both coils went out at the same time. And if it were grounding out, you probably wouldn't see any spark at all now. I'm thinking fuel related problem. Bad fuel pump, clogged or closed fuel vent, clogged fuel filter, etc. It could even be a stuck float valve from varnish forming after the motor has set a little while. You can bet it's something simple. It's all just guessing without a good spark test and tests of the fuel system. Holler back with some feedback and hopefully we can pinpoint the problem. I'm also suspicious of an exhaust leak since they're so notorious of having them.
Good luck with it,
JBJ

 

[62larkowner]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

well as far as fuel goes i unhooked the line from the carb , took filter out and cleaned all that , put filter back in and puped up primer bulb, it shot fuel out the hose that goes to carb,
sprayed carb cleaner into carb through inlet and it shot out jet in carb,
hooked line back up squeazed primer bulb n got nothing, figured with that it must be a vacume thing, idk much about 2 strokes

guess i nead to start dismataling carb idk

hopefully i'll have the headgasket n stuff soon so i can get 'er back togeather n start troubleshooting the carb

thanx for your help thow

will keep all updated

 

[samo_ott]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

They don't suddenly stop running at wide open throttle very often because of compression unless a dirt dauber nest under the cowl broke loose and the sand cut the rings out.

JBJ

What the heck is a dirt dauber? We sure as heck don't have them up north and I've only heard of them on this forum... And how the heck can they mangle the rings?

 

[jbjennings]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

Dang, don't you Canadians know anything? A dirt dauber is a wasp-like insect that builds its nest in any conceivable crevice it can find. They are a total plague around here. They will fly or crawl inside and build their nests which consist of mud that they "daub" on anything it will stick to. They lay their eggs in it and when they hatch out it gets sand from the dried mud everywhere. If it gets into your carb throat which is easily possible or your cowl where it can shake loose and get in your carb throat it can cause sand to be ingested into the crankcase where it will destroy the engine----or so I've been told by reliable sources. I've heard the sand can get in the cylinders and the grit destroys the rings and such. I've actually not seen it happen, Steve----you know how I like to regurgitate all the little bits of knowledge that you and Wayne and Frank lay on me from time to time. Anyway, I'm a firm believer in the "dirt dauber Danger". I'll post some pics of the critter's handywork so you'll see what I mean. I had one build a nest in the water pump indicator tube just yesterday and stopped it up completely on my barge. Luckily, I know to expect this and immediately found it. BTW, I put a new sierra rectifier on both of my merc 650's and they are now charging good. Yeehaw!
Sorry to hijack the thread but since it's already been 'jacked up I guess it won't matter.:redface:
Gotta hit the sack now so I can make it to SunDschool in the morning.
Later,
JBJ

 

[caddokid]

Re: 5.5hp Johonson Seahorse 1961 - Rated Compression

Sam it is one of the critters that us southern boys have to contend with. Had to remove some mud from one of them out of the fuel connectors to the 18 hp 'evinrude today. It completely cloged the fuel line to the fuel pump. Be lucky that you don't have contend with them or cottonmouths,watermoccisins, or alligators.

 

[samo_ott]

Re: 5.5hp Johnson Seahorse 1961 - Rated Compression

Re: 5.5hp Johnson Seahorse 1961 - Rated Compression

Dang. Sound like bad ole critters. Do they sting or anything else? JBJ, where's the pic?

And speaking of barges, I had to take mine outa the water today. 'Tis the end of the season