Merc 165/GM 250 engines

[jam39vw995]

The 165 merc is a 250 GM inline 6, what are the main differences between the one in the boat and the one in the truck?<br />I know about the manifold(s) already.<br /><br />I'm asking for this reason;<br /><br />The motor in the boat is quite old and is getting tired (450+ hours). I'd like to rebuild it but the boat is needed to commute. Would the motor from the truck work in the boat on a temporary basis while the real Merc engine is rebuilt?<br /><br />Thanks in advance.<br /><br />Jeff

 

[daveswaves]

Re: Merc 165/GM 250 engines

The truck motor will be missing a tab on the front for the marine motor mount. The truck motor will have steel freeze plugs, the marine probably brass, The cam in the truck motor will be unsuited for the boat, you would need an "RV" cam, internally the marine motor may have different bearing sleeves. Carb, alternator, fuel pump will be marine version and you would have to move these over to the truck engine.<br />Will it work? Sure but have you checked everything on your marine engine? 450 hours is not a long time for these engines, lots out there with 1250 plus. Lots of things can give you poor performance. Worn or fouled plugs, poor plug wires, dirt/crud/water in carb, vacuum leak at carb, plugged flame arrestor, cracked distributor cap, worn/pitted points. 500 pounds of barnacles on the bottom

 

[jam39vw995]

Re: Merc 165/GM 250 engines

Thanks Daveswaves.<br /><br />ya, I'm sure there are a number of things that would make this too much work. I was hoping. Next bet is finding a (very) cheap beat up boat with a average/good 165. <br /><br />As for performance.<br />We have installed new plugs, new cap, new wires, points looked good, no pitting. Dwell was right on. Timing right on. The carb could be the culpret alright. Should rebuild it.<br />There are so many things on this boat that need fixing it's driving me crazy because the owner, a good friend of mine, doesn't have the time to do it. If we could take it out of service for a while it would be much better, it's used to commute all year. Take the hydrolics, still don't work. If we could trim the leg properly I'd bet it would move a lot better, right now the leg doesn't go all the way down so the boat just doesn't quite get over the top on plane and I bet the leg trim is causing it. But I digress.<br /><br />What's concerning me right now is a low down vibration/knock. Sounds to me like a rod bearing.<br />It could be just a lifter or 2 but it seems lower down that that.<br />Anyway, I appreciated the reply.<br /><br />Jeff