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Questions and Update on my 1988 Larson 3.0 boat

braol911

Member
To All,
Thanks again to all who helped me with my shift cable repair. My update here includes my new headgasket story....

So I did the shifter cable without too much drama. We got the boat on the water and I noticed that it just didn't have the kind of power I'd expect. So I did a compression check. #2 and #3 cylinders were around 75 while #1 and #4 were within normal range. Sure enough, the head gasket was toast. I tore the engine down with my cousin and sent the head off for measurement and machining (with a 5-angle valve grind). They had to take .010" off to get it level!!!! Finally the boat goes like it should. It took us a few hours to r&r the head but the machining took about a week :(
Other snags I encountered along the way being new to Mercruiser repair: We forgot to reconnect the clear "overflow" tube from the fuel pump to the carb. The boat idled a little rough until I discovered this detail, now it is fine. The prior owner had a mishmosh of different sparkplug wires attached to the motor, now I have some high end Accel wires (yellow) and it looks good.
What else? I retrofitted a NAPA gold filter in place of the Quicksilver stock one. NAPA Gold or Wix, those are the only filters I use, call me picky. Changed the oil as I didn't know WHAT the p/o put in there. I went stock Merc oil (25w-40) with just a cap-full of Marvel's in there (hey, my '31 Ford still runs and that crap's been in there for years). I wired-in a depthfinder/GPS and a solar 12volt battery charger, bought a LOUD horn online, and will be switching over to all-LED nav light bulbs. Oh, and there is a USB charger where the cigarette lighter used to be.
Questions:
-Does someone make a high-flow air filter for the stock spark arrestor?
-Since the engine is a GM 4-banger, are there GM roller rocker arms out there that will bolt into the 3.0? How about ARP pushrods?
-Now I'm being silly but I'd like to get billet aluminum crank and alternator pulleys, but what type of compatibility is there between GM automotive stuff and the 3.0 marine engine...is there anything out there that would fit? Yes, billet pulleys are dumb but I like how they look. I think it'd be a riot to open the engine cover to show my buddies (who have Chrysler 454 V8's) my Mercruiser "Racing Version" 3.0 4-cylinder.

That's all for now. I'll keep everybody (who cares) posted!
 
Good to hear it came together ok

k&n makes some high high flow flame arrestors just check your dog house clearance before purchasing.

Cant comment on your other questions but wanted to make two comments

make sure your timing is correct at 1 def after tdc as 3.0s are known to blow head gaskets if timing is more advanced

also the tube from the fuel pump to carb inlet (on air horn right) should have no effect on engine performance as it won’t affect vacuum this is an overflow in case diaphragm on fuel pump ruptures it will dump fuel in carb creating a rich connection vs dumping fuel in bilge. There should be nothing in the tube any gas is a sign of ruptured diaphragm
 
"I'd like to get billet aluminum crank "

Never seen one of those...

Other than a turbocharger and/or nitrous, there's little you can do to make that boat go much faster with such a small motor. Dropping in a 350 SB Chevy would be your best bet!

Jef
 
"I'd like to get billet aluminum crank "

Never seen one of those...

Other than a turbocharger and/or nitrous, there's little you can do to make that boat go much faster with such a small motor. Dropping in a 350 SB Chevy would be your best bet!
Jef

Oh no, the literal police got me! Ha, ha... (I guess I should have said billet crank pulley and alternator pulley. (Didn't think I had to say 'pulley' twice to get my point across...my mistake.)

I never said anything about making my boat faster. I just like the look of billet aluminum pulleys (the unpolished kind). I also just like an engine that not only runs smooth and looks good, but is also more efficient. I know that roller rockers and a free-flow air filter would improve any engine. Heck, I already spent the extra cash on a multi angle valve job when I got the head milled, so why not go roller rockers? I also get great piece of mind from knowing that I got high quality parts in my engines...thus the question about ARP pushrods. I'm almost sure I can find those, I just need to pull a rod out and measure it...they must have a match. If they make rods for old Pontiac V8's they should have a match for the GM 3.0?

My quest for speed does continue though: I've always got my finger to the wind in search of an old boat with the Mercruiser 888 (Ford 302) set-up. We had an old '76 Crestliner (Pre-Alpha) with that set up and it was SWEET.
 
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