what caused this?/'57 35 hp seahorse.

[rolmops]

The other day on the lake going at wot suddenly went down from 4500 to 2900 rpm.When I came home I took off the flywheel, checked the coils and points.Everything seemed to be fine.I checked for spark and the spark on both cylinders will easily jump half an inch.I checked the fuel lines and connectors for obstruction and found neither dirt nor leak.The only thing thing different was that I changed from regular tc-w3 to synthetic tc-w3.Both mixed at 1:32.Could this be the issue or is it time to clean the carb or maybe even check the reeds?<br />Just yesterday I tried to start it again and I ended up starting it with the ropestarter after having drained the battery trying to start it.<br />Thanks in advance for your opinions and help.

 

[rwise]

Re: what caused this?/'57 35 hp seahorse.

How do the plugs look? Maybe the synth cleaned out some crud and fouled the plugs? Just a thought!

 

[K Hultgre]

Re: what caused this?/'57 35 hp seahorse.

Have you tried squeezing the bulb while underway to see if the fuel pump is getting weak. Also the vacuum line for the fuel pump that runs past the head can either rub a hole in itself or lay against the head and melt a hole. What does the fuel bowl and filter look like (gunky, clean)?<br /><br />Check spark again with the plate fully advanced and somewhere inbetween. May have rubbed one of the plug wires through and could be dropping a cylinder when the plate is turned just right.<br /><br />Do a compression check.<br /><br />We had one of these on the first boat my family owned. By the time I was 13 I knew how to disassemble, repair and reassemble this motor. It's been 24 years since then but I can remember it like it was yesterday (what did I do yesterday?). The motor had been run in Saltwater for 10+ years then in freshwater for another 10. Been through 2 teenage girls (older sisters)(did not know the concept of premix) then finally the lower unit went kaput, so we upgraded to a mid 60's 65HP Johnson, it could drink the gas at WOT compared to the 35.<br /><br />Good luck,

 

[Walker]

Re: what caused this?/'57 35 hp seahorse.

First thing to do is a compression test.

 

[R.Johnson]

Re: what caused this?/'57 35 hp seahorse.

The 1957 35 HP did'nt have a fuel pump with primer bulb, It used a double line, pressurized tank. One thing it may have as I recall is a vacuam switch wired to the ignition to shut down one set of points to keep the RPM's down if you were to shear a pin. If that vacuam switch has a hole in the diaphram, or the hose itself is broken, you could have the condition you discribe.

 

[Paul Moir]

Re: what caused this?/'57 35 hp seahorse.

I'm with R.Johnson and rwise on this - if it dropped suddenly it's probably ignition. Try disconnecting and isolating the two low tension magneto leads and running it - that should eliminate the vaccum switch, keyswitch, wiring, etc on that end of the system. 'Course you'll have to choke it to kill it.<br />No signs of oil around the top crankshaft seal right?

 

[R.Johnson]

Re: what caused this?/'57 35 hp seahorse.

Paul: You can't just unwire the switch, if the hose is broke, or the diaphram torn, you will have one heck of an air leak.

 

[Paul Moir]

Re: what caused this?/'57 35 hp seahorse.

I ment for rolmops to remove the wire from the top of the vaccum switch that runs to the mag plate, and break open the quick disconnect on the other lead (if present) under the hood. That should isolate the ignition system from everything else. I should have been more clear.<br />Ah, yes - I see what you mean about an air leak. I wasn't thinking that way, but rather in the electrical direction. I just assumed the 35hp used an oriface on the manifold vac hose nipple like later ones.

 

[rolmops]

Re: what caused this?/'57 35 hp seahorse.

Thanks a lot for your help guys.I just checked compression and it reads 120# on the top cylinder and 0# on the bottom one so I will be spending quality time with my 12 year old in the garage and not on the lake.I'm lucky that I did not take this engine out to Cape Anne.Please help me hope it is only a blown head gasket.

 

[rwise]

Re: what caused this?/'57 35 hp seahorse.

ouch, well it's for the your son to get into things like this, good luck!

 

[Chinewalker]

Re: what caused this?/'57 35 hp seahorse.

Hi Rolmops,<br /> FIrst thing I would check would be the head gasket. It's not uncommon for those OMC Big Twins to blow them out now and then. That would also explain the relatively quick loss of power. Were there any beads of water on the spark plug?<br />- Scott

 

[rolmops]

Re: what caused this?/'57 35 hp seahorse.

Thanks again guys.<br />It was the head gasket so for 15 bucks and some elbow grease we're back in the water.It is amazing how clean that lower cylinder looks now.But it is back at 120 psi, so it seems I should be dancing a jig.All that is left to do is check the impeller and cooling lines for obstructons that may have caused this.<br />Thanks again.

 

[DJ]

Re: what caused this?/'57 35 hp seahorse.

rolmops,<br /><br />That is FANTASTIC news.<br /><br />Don't ya love it when one turns out like this?

 

[rwise]

Re: what caused this?/'57 35 hp seahorse.

And then some fresh bait and....