Mercruiser 3.7 rebuild? or repower

[shadetree_fish]

Hey guys, I have a 1984 chaparrall 187 XLC with a merc. 3.7 closed cooling system. I traded VW parts for the boat/motor/ & trailr. The boat has been sitting for 10years & was parked becuase it overheated & blew the engine possibly only a head gasket and/or cracked head??? It is 100% complete. should I repower or rebuild if the block & head are good? I have started a full redo of the boat including Stringers & Transom. Yeah i know, big job but never gonna learn just reading & surfing the web!!! :redface:

thanks in advance to all replies!

Mike in Fort Worth

 

[stonyloam]

Re: Mercruiser 3.7 rebuild? or repower

If the block and head are good, the easy answer is rebuild. That would be by FAR the least expensive and time consuming way to go. They have pretty strong bottom ends so if the cylinder walls are OK, you should be looking at only head work, pretty straight forward repair. You probably would want to hold off on hull repairs till you determine the engine health as you would have to make significant changes (stringers motor mounts) to put in a different engine. Let us know what you find. Good luck.

BTW there is a restoration of that exact boat with photos in the restoration forum here. http://forums.iboats.com/showthread.php?t=332712

 

[shadetree_fish]

Re: Mercruiser 3.7 rebuild? or repower

Thanks stoney, As far as re-powering if needed, wouldn't a GM/merc120 or 140 4cyl.bolt in and work with the out-drive? I'm certainly not a know it all! but i do know a little about engines. Besides, no matter what the condition of the engine, I'm going to strip the deck and replace stringers & transom if needed.I like the style of the boat & I'm gonna convert it to what i want in a boat, fishing pleasure, tubing, just cruising.
I like the 4bangers. I currently have a 04' glastron sx 175 thats volvo I/O and that thing wil do 38-41mph trimmed out with a medium load & half tank of fuel, I can almost run a full 3 day weekend on Texoma tubing, fishing, riding the waves!!!
This older boat is a project that I want to do if needed, to teach myself how its done and maybe save a few other boats later on.

 

[stonyloam]

Re: Mercruiser 3.7 rebuild? or repower

I am not sure about the motor mounts on a 120 or 140, but the problem is that they are a significant step down in power and are heavier than the 3.7, and the outdrive gear ratio would be wrong. It originally sounds like a head gasket problem. My main concern is that after 10 years you may have rust in the cylinders. What I would do (I am no mater mechanic) is pull the plugs, add some oil to each cylinder and see if you can get it to turn over, either with the starter or by hand. If it is free, a fix may be as simple as a head gasket. There are a couple of other concerns with the 470 (3.7) like cam seals, and making sure you have a 4" heat exchanger, but since you will be pulling the engine anyway they can be easily taken care of. If you can get it running that should be a good little engine for that boat. Good on gas and 40+ MPH. Welcome to the "470 club".

 

[Rocky_Road]

Re: Mercruiser 3.7 rebuild? or repower

Thanks stoney, As far as re-powering if needed, wouldn't a GM/merc120 or 140 4cyl.bolt in and work with the out-drive? I'm certainly not a know it all! but i do know a little about engines. Besides, no matter what the condition of the engine, I'm going to strip the deck and replace stringers & transom if needed.I like the style of the boat & I'm gonna convert it to what i want in a boat, fishing pleasure, tubing, just cruising.
I like the 4bangers. I currently have a 04' glastron sx 175 thats volvo I/O and that thing wil do 38-41mph trimmed out with a medium load & half tank of fuel, I can almost run a full 3 day weekend on Texoma tubing, fishing, riding the waves!!!
This older boat is a project that I want to do if needed, to teach myself how its done and maybe save a few other boats later on.

I have a 470 with a possible head gasket issue...and all the research that I did tells me that the easiest swap is to the 3.0L, since it mates with my Alpha drive without any changes. The front mount would have to be fabbed into the boat, however.

The HP ratings for the 3.0L are not that far from the 470, since the 470 was rated from the flywheel and the 3.0L is rated from the prop. They are, in the real world, very close.

There was a website for a business that specialized in replacing the 470 that made all of this very clear...I will try to find my link to them.

P.S. My second boat has a 3.0L (which is why I haven't done anything with my 470), and I love that engine...rock solid and simple enough to keep running perfectly from my driveway!

Happy boating!

 

[shadetree_fish]

Re: Mercruiser 3.7 rebuild? or repower

Yeah, I havent had time to fool with them this week, but I'll try that oil in the cylinders and see what happens, Ill let yall know. I'll post some pics asap.

Oh BTW, I guess I should intro myself too! I'm new to boat "Re-building" but have had 2004 glastron sx175 that i bought new in 2004, all I have done is general mait. & tried to keep it up & going AND ALSO KEPT IT REAL CLEAN!!! So this whole building/rebuilding thing is quiet alot to take in and figure out!!! anyhow, hello to all and as I get going I'm sure i"ll have a lot of Q's

have a good day to all, Mike