73 mercruiser running problems

[taramak]

just bought the boat, had it out on the lake and putted around for about 1 hour at about one quarter throttle, then took it for spin around lake only for about 15 minutes, when slowing down, the enging died and had tough time starting again without choke. got it started but had to use choke even when warm. once running if i shut the choke off it would quit. but if i gave it throttle,it would run great at top end but wants to stall when i slow down to come in to a dock? i have put a premium in it but did not take the tank out to clean it completely. new filters all around, any ideas it is 120 hp inline 4

 

[mkast]

Re: 73 mercruiser running problems

i have put a premium in it

Waste of money.
Troubleshoot the carburetor/rebuild.

 

[dingdongs]

Re: 73 mercruiser running problems

which carb but stripping carb is high on the agenda as well as checking fuel pump on block and water in filters etc etc.

 

[taramak]

Re: 73 mercruiser running problems

is premium gas a waste, i am not a expert in this, just going by what the label on the tank says, 93 octane minimum. i am also looking for a place to buy a rebuild kit for the carb, and how do i find out what type of carb it is! it is a gm engine i am told. inline 4

 

[mkast]

Re: 73 mercruiser running problems

just going by what the label on the tank says, 93 octane minimum.
and how do i find out what type of carb it is!

I think that label was installed in 1973.
Not knowing which four cylinder engine, I'm guessing the compression ratio is around 8.5 to 1, 87 octane will be more than adequate.
Is there a tag on the carburetor?
Engine serial number may help.

 

[taramak]

Re: 73 mercruiser running problems

i will get all the data i can fromthe engine and boat plate however the spec plate is 3/4 blocked by the throttle box. I will try to get as much info as i can. I will post after work at 4:30 I thank you for your time.


i think i found the problem, while looking for numbers on the carb which only says GM 2 jet(is this original, any good?) i have noticed that two of the four screws holding the upper part of the carb are missing and is loose, as well, where the choke pin goes through the intake and out the side into another module, there are two screws that are loose or broke and it is loose on the side of the carb. what would this module be for? i am hoping that when i replace all the screwss with new ones this should solve the problem. whicfh would make sense to me and correct me if i am wrong, wheni give it throttle, it sucks air and would seal the carb to the intake manifold, and it runs great, and when i ease off coming into a dock it would come loose and suck air in the bottom and screw up the mixture. I am not a mechanic, am I off base here? i guess i wont know until i try it. I really do appreciate your time and if i have more issues i will be back. these forums are the best things to come along in a long time. my hat goes off to those who have the knowledge and are willing to share that knowledge with others so that they may be able to enjoy this hobby without having tosell their first kid!

 

[taramak]

Re: 73 mercruiser running problems

there is no tag on the carb, only "GM 2 jet" engine serial number "4156506" does this mean anything? i know nothing about the engine, what model it is or anything you could tell me would be great. also, please read my other addition to my last post. thank you again for your time and knowledge. it is greatly appreciated. i have to girls aged 9 and 11 and they can't wait to get back in the boat! this is our first bigger boat, last one was 12'aluminum with 9.9hp. a little step up. last week end was our first time in it.

 

[azacher]

Re: 73 mercruiser running problems

GM 2 Jet usually refers to a Rochester 2 barrel, very, very easy to rebuild. Kit usually runs about 25$ from West Marine (just finished mine last week, massive improvement!). And it sounds like you are on the money with the air leak at the base of the carb, that would also explain why the choke was helping it run right, you were blocking the air from the top, so it was sucking it in from the bottom to compensate...definitely follow through with a rebuild, new filters (one in carb, one in pump at the very least), and re-attachment of the carb to the motor. Also a good idea to buy all of your filters in pairs, one to use and one to have for next year!

 

[taramak]

Re: 73 mercruiser running problems

thank you, i am still looking for dealer up here in the "great white north"(Canada), eh!

 

[Doernuth]

Re: 73 mercruiser running problems

That carb rebuild kit is a common part. Call your nearest Mercruiser dealer or repair shop they may have it in stock. You can also order online at West Marine, overtons or Iboats. Not sure how they ship international though.

Good luck and let us know how it goes. I have three of those carbs, two on the boat and a spare to rebuild at the moment.

 

[taramak]

Re: 73 mercruiser running problems

called my local dealer, kit is $80 plus tax, same ol same ol for us canadians, everything is more than double than in the states! i will check the sites you gave me and i do appreciate the help. I am going to test it out this weekend with just fastening the carb and see how it goes. i will let you know what happens.

 

[taramak]

Re: 73 mercruiser running problems

screwed down the carb, plug wires were shot, seems to run good on water muffs, didnt get time to put in the lake. water pump is making high pitch noise, ordered one, here on wednesday, i'll put it in and get to the lake this weekend. was told you can't replace bearing on water pump, have to replace the whole thing? is this common?

 

[cr2k]

Re: 73 mercruiser running problems

Are you talking the water pump (in the lower leg of the outdrive) or the circulation pump (front of engine)?
Marine circulation pumps usually have sealed bearings and stainless impellers, some even have bronze housings.
Is the belt too tight? This is usually what wastes the bearings.

Replacing the whole unit is common, having to replace it is not that common, but it happens.

 

[taramak]

Re: 73 mercruiser running problems

I have fixed the carb issue, fastening it properly was all it needed, i have replaced the wires, runs very well on the water but I still have a high pitch noise. Would the gimbel bearing make a noise up in the engine compartment? I have just replaced the impeller and found alot of muck in the lower cavity in front of the housingfor the impeller. it looks like it is where the gear selector is located. how would it get in there?

 

[JBRJ65]

Re: 73 mercruiser running problems

I'm no expert but have lived every issue you have spoken about in this thread.
The high pitch squeal could certainly be the gimbel bearing but before you assume I recommend making sure you don't have a bad belt or bearing on the front side of the engine. Is the squeal always there or just under load ? Have you lubed the gimbel bearing?
I ask this because I have the same engine and had same issue. Lubed the gimbel and squeal went away. Ran for couple hours and squeal came back as I figued it would, replaced Gimbel and life is great... Check those belts, alternator, water pump, etc.. first

Just my modest opinion