Mercruiser swaps

[mhicks]

I am new to boats and I was out Sunday going about 3/4 throttel and a loud knock started and the engine died. I cranked it back up and it had a knock like a rod bearing. I slowly drove it about two more miles to the boat ramp and loaded it up.
It is a 170 HP mecruiser in a 1986 Century (19'6"). I started looking for used motors and found a 1973 mercruiser motor. It looks a little different than mine and was wondering if anybody would know if this motor would replace mine without any changes.
I was talking to the guy that is storing the boat for the guy that has the motor for sale and he said he had a gimble bearing make the same noise as a rod bearing. Have any of you heard this before? It is gonna cost me about 2500 to have the engine pulled and rebuilt or 350 to replce the motor if I do it myself and this engine will fit. They are both Mercruiser 170 HP inlne 4 cylinders.
Thanks,
Mike

 

[xltier]

Re: Mercruiser swaps

I am new to boats and I was out Sunday going about 3/4 throttel and a loud knock started and the engine died. I cranked it back up and it had a knock like a rod bearing. I slowly drove it about two more miles to the boat ramp and loaded it up.
It is a 170 HP mecruiser in a 1986 Century (19'6"). I started looking for used motors and found a 1973 mercruiser motor. It looks a little different than mine and was wondering if anybody would know if this motor would replace mine without any changes.
I was talking to the guy that is storing the boat for the guy that has the motor for sale and he said he had a gimble bearing make the same noise as a rod bearing. Have any of you heard this before? It is gonna cost me about 2500 to have the engine pulled and rebuilt or 350 to replce the motor if I do it myself and this engine will fit. They are both Mercruiser 170 HP inlne 4 cylinders.
Thanks,
Mike

sounds like you have a mercruiser 4 cyl.does it have the closed cooling system. thats the only 4 cylinder that had that much h.p.a 1973 4 cylinder is only gonna have about 120 h.p.they were a chev. engine.not much power for a nearly 20ft. boat.they only used the merc engine for a few years.veru troublesom.you would want a v-6.but it would take some extra exhaust work.try removing the drive and start the engine to check the noise.with a bad rod bearing you should have low oil pressure also.hth

 

[mhicks]

Re: Mercruiser swaps

The guy said it was a 170 HP on the '73. They are both closed systems. The heat exchanger on the '73 is 3" where mine is 4". They look pretty much like the same engine. Have you ever heard of a gimble bearing sounding like a rod knocking?
I do not have an oil pressure gauge, only a light. I guess I could buy a cheap one and just hook it up temp.
Mike

 

[Haut Medoc]

Re: Mercruiser swaps

Pull it out of the water & pull the drive, if the knock is still there, it ain't in the drive......
They both should be the same block & interchangeable......
Merc went to the 4" exchanger after they figured out the 3" wasn't quite doing the job.....
If you can get a running 165/470/488 for $350, jump on it.....

 

[180shabah]

Re: Mercruiser swaps

If you can get a running 165/470/488 for $350, jump on it.....

Agreed - you will have spare parts if needed. Make sure you use the 4" heat exchanger that you already have.

 

[mhicks]

Re: Mercruiser swaps

Thanks for the help. If there are any other opinions out there I would like to hear them.
Thanks

 

[180shabah]

Re: Mercruiser swaps

Sorry I didn't catch this earlier, You really need to determine exactly what this guy is selling. The 3.7 was not introduced until 1976.

As for other options, a current 3.0 is a decent and fairly simple swap for the old 3.7. If your 3.7 has the 2bbl carb on it then the power is about the same for both engines. Although the 3.0 will have a little less torque down low.

 

[xltier]

Re: Mercruiser swaps

The guy said it was a 170 HP on the '73. They are both closed systems. The heat exchanger on the '73 is 3" where mine is 4". They look pretty much like the same engine. Have you ever heard of a gimble bearing sounding like a rod knocking?
I do not have an oil pressure gauge, only a light. I guess I could buy a cheap one and just hook it up temp.
Mike

if you take the drive off and it still nocks then i guess it really dont matter.350.. is cheap if it runs good.definatly do the 4 inch.

 

[mhicks]

Re: Mercruiser swaps

I found out that it is a 1976 midel. So, it should be a direct replacement then?

 

[180shabah]

Re: Mercruiser swaps

I found out that it is a 1976 midel. So, it should be a direct replacement then?

yes