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1976 Sea Horse 55 hp

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Rocketman14

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I found a 1976 55 hp Sea Horse motor for $350,and it looks like a good motor. I know, I broke the golden rule buying a motor and not hearing it run but for $350 I took the gamble, plus it had all the controls to go with it.
I hand spun the flywheel and the motor felt good and tight and there was no slack in the rods that I could feel. Each compression stroke felt fairly even as far as I could tell. I also shifted it from forward, to nuetral and into reverse and spun the flywheel and verified that the prop turned in forward and reverse.
So by this weekend I will have it on the boat and will begin rebuilding the carburators, new water pump, and basically do all the maintenance one would normally do on a motor that has been sitting for 5+ years.
I plan on doing a compression check and would like to know what the minimum compression value would be. I know, I should have did that before buying the motor but I was out of town when I ran into the deal and didn't have my tools with me.
Also how good are these motors? I can find no history on their reliability but I do remember seeing them on a ton of boats in the late 70's on.
A friend told me that they were a bulletproof motor but that is all I know.
 
Good motors. The older (50hp) versions had some trouble with busted pistons, but as far as I know that was fixed by 1976.
 
They are a high revving motor and many suffered from bearing failures.--------------These motors must be looked after properly and run with a tachometer / proper propeller.
 
Thanks for the replys men! So what would be the minimum compression value for a good running motor? Like I said I will do a compression check as soon as I get the motor on the boat and would like to know what it should be.
The motor was on a pontoon boat and used mostly for putting around on a Michigan lake per the previous owner. And it appears that the motor has been maintained because all of the grease points show that they were lubricated regurlarly and the spark plugs look to be new. Like I said in the previous post, the rods and crank felt like new when I hand spun the flywheel back and forth, and could hear no slop at all. There was no side play or slop at the flywheel either. It appears to be a good tight little motor but I know there is only so much you can tell when turning things by hand.

Again, what would be the minimum compression?
 
There are no values published.----There are too many variables and different gauges too.---------With my tester I would be looking for 150 PSI.-------The most important thing is that they be the same.-------Hopefully the previous owner had the correct prop for the pontoon boat.------You will have to verify and test to make sure the prop is correct for your boat.
 
kimcrwbr1 said:
Fog the motor good before you try to fire it off. Pull the plugs and spray fogging oil or seafoam in the cylinders then have someone turn the key as you hold the throttle butterfly fully open and spray the fogging oil in the carb as your cranking the starter. Do a spark gap test with a spark gap tester it should jump a gap of at least 3/8 inch gap brite blue snap. Clean all the connectors and grounds good with a small wire brush and put connectors together with dielectric grease. Sounds like a good score even if the powerhead is shot you can sell the controls and gearcase for a substancial profit if in good condition. Take your time and dont connect the battery until you are certain the wiring is correct. it takes a split second shorting the kill wire to battery pos to cook the switchbox.
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Yeah I felt that it was worth the risk at $350. And to make the situation even better, the boat I am putting it on was free. The boat is a 1968 Glaspar Avalon and has been restored, new carpet, good seats, and the paint is like new!
The boat had a 1968 55 hp Evinrude and I am going to put the prop from the old boat on the Sea horse if it will fit. I am thinking the splines will be the same but am not totally sure until I try it. Since the old motor was 55 hp as well, if the prop fits the newer motor, it would theotetically be the right prop for that boat and horsepower...........I hope!
I am planning on soaking the cylinders with Sea Foam deep creep for a couple of days before mounting the newer motor to dissolve the carbon. Does anybody know if a prop from a 68 Evinrude will fit on a 76 Sea Horse both 55 hp?
I am trying to build a good running boat for less than $800 just to see if I can do it. We plan on putting around the bay in Lake Eerie and rarely running WOT, just putting and enjoying the water.
 
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Well I am going to put a tach on the boat since it has the tach plug right on the front of the control unit, and feel that will help with getting things right. So after I get the motor tuned well enough to runs 100% RPM's, how will I know if I have the right prop? Do you then go by the speed of the boat versus RPM's?
 
So if she won't rev to the maximum WOT RPM's, I have the wrong prop, and conversely if it rev's to max RPM's and isn't going fast at all, I again have the wrong prop! It seems to be one of those not to exacting sciences, but I do understand what you are saying!
 
An original prop from a 68 motor ( 3 cylinder ) likely will not fit on the 2 cylinder motor.------------The early 3 cylinder had a smaller prop shaft.
 
Well hopefully the prop already on the motor will work. My boat should be a lot lighter than a 20' pontoon boat so I guess it's up to the rpm testing now.
 
Well I looked up the dry weight of the boat, and calculated everything else. It looks like the weight with just me in the boat will be around 1371, and max rpms for my motor are 5500 rpm's.
I am going to mount a tachometer on the boat and will try not to exceed 5250 rpms so as not to over rev my old motor! I am planning to only cruise at around half throttle in this boat and have no desire to go fast, so if it can get to even 5000 rpm's I will be happy!
 
Looked it up in the factory brochure just to refresh my memory and it says ----" 55 hp at 5500 rpm ".------Full throttle operating range is 5000 to 6000 RPM.
 
Don't know if these two engines relate to your questions. I had a 1975 115. It was a very reliable engine and had not had any major problems, power head, carbs, electrical, lower unit. Lower unit seals and water pumps was about it. Also, it was used mostly in saltwater. The compression on the 4 cylinders ran between 85 and 95. Before running the compression test, make sure the battery has a good charge and remove all plugs. Might want to fog a little lube in the cyls before cranking.
 
Thank you very much for all the help guys. I have learned a lot already, and now feel like I'm on my way to being a competant marine mechanic............well sort of!
I was looking at the Sea Horse motor last night and realized that the little clips that hold the shifter and throttle cables onto the levers are missing. It has the square shaped control cables and i sure hope I can find some of those clips. I could probably make some but would much rather have the factory clips.
Can I order these from Marine Engine .com? I looked in the cables section and I think the cables are the Teleflex 400 series, but see no mention of the keeper clips that hold them onto the attachment arm!
 
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Rocketman14 said:
Thank you very much for all the help guys. I have learned a lot already, and now feel like I'm on my way to being a competant marine mechanic............well sort of!
I was looking at the Sea Horse motor last night and realized that the little clips that hold the shifter and throttle cables onto the levers are missing. It has the square shaped control cables and i sure hope I can find some of those clips. I could probably make some but would much rather have the factory clips.
Can I order these from Marine Engine .com? I looked in the cables section and I think the cables are the Teleflex 400 series, but see no mention of the keeper clips that hold them onto the attachment arm!
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Well I called Marine Engine and they found the clips I need....................whew!
 
Update: I got the new engine mounted on the transom and am planning on installing the new water pump impeller this weekend. I have a manual on this engine and it does not show much detail on how to disconnect the shifter rod when dropping the lower unit. Do any of you guys remember how to disconnect the shifter rod on a 1976 55 hp Sea Horse motor? It does not have the access plate for the shifter rod coupler!
 
Remove the starter !----That makes it easier to find the specail pin that connects the shift rod .------7/16" socket required.
 
racerone said:
Remove the starter !----That makes it easier to find the specail pin that connects the shift rod .------7/16" socket required.
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Okay, so I remove the special pin that will allow the shift rod to drop, then when the lower unit drops about an inch, I disconnect the coupler on the shift rod...........correct?
 
Not correct.----You remove the pin and the lower unit comes off.--There is no other connecter on the shift rod !-------Also do not turn the shift rod either !
 
Update: I needed a silencer because the engine didn't have one when I bought it, si I got on E-bay and got a silencer and 2 carburators for $75 bucks. The carbs are definately for a 55 hp 76 Sea Horse, but they have the intermediate jets on top of the carbs just in front of the mounting flanges. Everything else is the same but have not disassembled them and checked the jet / orifice sizes.
So, my question is, since I am going to put new carburator rebuild kits in, which set of carbs should I use? Are the carbs with the intemediate jets any better than my originals that do not have them?
 
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