1984 mercruiser 3.7 - need info on what to replace for tune up

[kevinstan]

I just obtained a new boat on a trade. I got a 1984 Larson senza. Has a 3.7 mercruiser in it. I don't know much about these i/o motors as I have never had one before. All my previous boating experience is with smaller outboard motors. I know I will need to winterize the motor also, which I will have questions about later I'm sure - but for now I am really wanting to know what all I can replace and update for a good overhaul and tuneup to make sure it's ready next spring. The motor seems to run pretty good without any flaws, but since I have never owned one before I need to know how to maintain it. Any help would be greatly appreciated. New filters or hoses or belt ? What all does everyone do to keep these motors good and running strong ?

 

[stonyloam]

OK , first thing, since it is getting colder, check the antifreeze in the reservoir to make sure it is about 50/50 automotive antifreeze. You can get a cheap tester for a few bucks. If that is OK then all you need to do to winterize it is pull the aft plug on the underside of the heat exchanger to drain out the seawater ( if antifreeze comes out you pulled the wrong plug). That is it, done in five min., you can fog it if you like, but I never have with mine. Other stuff, with a 470 it is alwayse a good idea to do a compression check just to make sure the head gasket is in good shape. Other engine stuff, new points are a good idea (you can go with a Petronix electronic ignition if you like, but is not necessary). Check your plugs and plug wires. The other thing that is very important is that the impeller in the raw water pump in the out drive must be kept in good shape, that means a new one every other year. You will want to learn how to pull the outdrive to check the gimbal bearing, and grease the u-joints, as well as changing the impeller. Yo will need to pick up a Mercruiser alignment tool (e-bay). If you have any questions, come on back here and we can help you out. Oh yeah check the voltage output of the regulator. Should be about 14v. If way high or way low, consider an alternator conversion. Welcome to the "470 Club"

 

[kevinstan]

Thanks for the great information. I have heard these are great motors as long as they are properly taken care of. Since this is my first I just want to make sure everything is right. Would you suggest changing the oil filter or plugs / wires ? Mainly because the guy before me said nothing had been changed in about 3 years prior to me purchasing it. Should I change the fuel filter or would it be time for a new gimbal bearing ? I just want to do as much of the small tuneup stuff as possible before next spring. It does have a new water pump in the outdrive already so I don't need to worry with that as of right now. Any other thoughts on stuff that needs done or replied to ensure good operation ? And lastly, does this motor have a fuel - water seperator on it ?

 

[stonyloam]

Yeah change the oil and filter, I use a Fram PH 13 (whole list here: http://www.breezeworks.net/cgi-bin/MBoard/forum/display_topic_threads.asp?ForumID=1&TopicID=1473 ), for oil I use Rabolo 20 W 40 from Tractor Supply (same oil I use in my diesel equipment). Plugs and wires? Pull them and take a look, for the wires try starting the engine at night, and mist a little water on them from a spray bottle. If you see any little blue sparks jumping off of the wires or it starts to miss, time for new wires. There is a fuel filter in the fuel pump and a screen in the carburetor inlet, I have never messed with mine, and it has only been 24 years LOL. The engine did not originally have a fuel water filter, but a po may have added one. A gimbal bearing May last a long time, the way to check it is remove the out drive and stick your fingers in and turn it. If it turns perfectly smoothly with no roughness you are OK. You will want to pick up a couple of tubes of grease quicksilver 2-4-C and extreme grease, and a couple of inexpensive grease guns. Use the 2-4-C on the parts exposed to water (prop shaft, gimbal ring pins) and the extreme on gimbal bearing, u joints and driveshaft where it goes into the coupler. Go to boatinfo.com and find manual #8 (engine) and #6 outdrive. That is about all I can think of for now. Good luck.