1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Your engine does NOT call for an MR43S, it calls for an MR43T, the non marine version is R43T This assuming you have a 3.0L engine and not a 3.0LX model. Do you have your engine serial number handy?

If you get the right plugs, it might start easier. Did that MR43S info come from that clymers manual you have?

Your right, it is MR43T. That info came right off the decal on the cover of the flame arrestor. The serial number i do not have handy, it starts with OF, the label on the engine says 3.0L. When i get home tonight, i can furnish the serial number of the engine and carb.

 

[Don S]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Don't need the carb number, just the serial number. If the engine is an LX, it would take a completely different plug.

 

[ktbarrentine]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Years ago , (25-30 ) The AC spark plug company did make a marine type spark plug . There might have been some substance to it, but I remember the spark plug body was either painted silver for corrosion resistance and the porcelain had blue rings located on the ridges . It was a modified number of the regular plug number . An AC plug for marine use would be MR45S. Broke down it would be M , marine , R resistor , 45 , heat range and S meaning it had a shorter porcelain tip. I'm sure this was a big marketing gimmick , bit it worked back then . True , there are no marine plugs any more but, marketing gimmicks last quite awhile

Refresh my memory.... "S" is standard seat (i.e. metal ring), and "T" is tapered seat (no ring)? The length of the porcelain in the center electrode is predicated by the heat range? I use MR43T. I had MR44T when purchased from the original owner (a mercruiser 5.0L), but was advised to go back to the lower heat 43Ts as that is what the manual calls for. So far, so good. Original owner cant explain why he had 44Ts in there (engine is 22 years old).

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Don,

The engine serial number is OF144286.

 

[Don S]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

It is just the 3.0L, not the LX and you do need the MR43T spark plugs.

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

I verified that i do have MR43T.

There is no gap on these since they are the "center fire". When the carb was apart, the float weighed in at 8.4g, the book siad max wt 9g. Height was set with gasket to 3/8". I do not see any fuel leaking into the carb after shutdown, watched it for about 5 minutes. The throat looks wet though. When you go to crack it back up, while cranking the engine, throttle at idle, you can see gas coming into the carb. It will fire and run rough for a few seconds before smoothing out.

 

[Don S]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

MR43T plugs are NOT center fire. I don't know what you have there, but it's not the right thing. Post a picture of one of your sparkplugs.

It will fire and run rough for a few seconds before smoothing out.

It's carbed, that's typical on those engines.


Here is a picture of the MR43T spark plug

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Don,
I apologize, I am working on three different engines right now and i got confused on what i had. I have regrouped and the plugs are in fact MR43T with the gap set at .035. They are identical to what you have in your pic. It will be Friday before i launch again and have a chance to run it under load. Do you have any more suggestions as to what if any thing to troubleshoot/check next?

 

[fat fanny]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

I have run both mr43t and the ts which I currently use and have had more success witht he ts over the past 10 years

 

[amizelle]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

I'm following this thread closely as I have the exact same problem...

 

[achris]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

..... (Float) height was set with gasket to 3/8". I do not see any fuel leaking into the carb after shutdown, watched it for about 5 minutes. The throat looks wet though. When you go to crack it back up, while cranking the engine, throttle at idle, you can see gas coming into the carb. It will fire and run rough for a few seconds before smoothing out.

Try setting the float height to 7/16". The 4 bbl Webers used on the 4.3 V6s of the same era had the same problem, fuel dripping after shutdown. You can't see it because the fuel will either drip directly down from the venturii, or out of the idle and progression holes. Either way the engine gets flooded. Setting the float level 1/16" more will lower the fuel level in the chamber and reduce the effect of capillary action, the main contributor to the flooding... It won't lean the fuel mixture enough to have any effect on the engine....

Chris....

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Chris,

I am launching in about an hour and see what happens. If still having problems, i will pull the top off and reset the float to 7/16" and try it. I suppose it seems like a minor issue to some, but when i am towing skiers and tubers we try and load from the swim platform and i shutdown. That is when i have the hard start problems the most. I am willing to try anything that seems reasonable and i have learned a lot from this forum.

 

[dollarten]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Chris,

I am launching in about an hour and see what happens. If still having problems, i will pull the top off and reset the float to 7/16" and try it. I suppose it seems like a minor issue to some, but when i am towing skiers and tubers we try and load from the swim platform and i shutdown. That is when i have the hard start problems the most. I am willing to try anything that seems reasonable and i have learned a lot from this forum.

IF process repeats itself , I would try to swap out the carb . Numerous attempts at redoing the carb would point in that direction . There could be some internal flaw in the carb

 

[dollarten]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

MR43T plugs are NOT center fire. I don't know what you have there, but it's not the right thing. Post a picture of one of your sparkplugs.



It's carbed, that's typical on those engines.


Here is a picture of the MR43T spark plug

The center fire plugs you are talking about were a short run item . The did not have an adjustable gap , like yours does . They have multiple ground electrodes aiming to the center tip . They are also flush with the center electrode . The marketing point here was that the spark was not being shrouded by the ground electrode . They said it would make the spark more visible to the air/fuel mix for better combustion . It sounded good but doubts prevailed if any improvements were noted

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Just got home after a day of fishing. Left the ramp at 0900, run to th efishing hole and shut down. Restart was good, run to our favorite eatery and shut down. Restart was still good. Run back to the fishing hole and shut down. Restart was good, run to the marina, shut down for fuel. Restart good, loaded on trailer. Came to house (15 minutes) and again, restart is good. As of right now, it does appear that wiith the resetting of the float and fresh fuel filter/plugs and all, it might have fixed it. I plan on launching again in the morning if the weather holds and will run it hard and try it again. Today, we had a full load, and was running at cruising speed of 4000 rpm, (30 MPH) for 30-45 minutes between shutdowns, letting it sit for between 5-15 minutes except at the eatery where it sat for 1 hour. All restarts were fairly quick, with just advancing the throttle just past idle. Thanks to everyone, especially Don for the tips and helps.

George

(My Mistress)

 

[ckirk]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

HARRITWO your last post was March 23rd; is your boat still running well?

I have had the same problem with my 3.0L for a while. What would you say was the final resolution to this probelm? Reading the total thread it sounds like the resetting the float height did the trick. I plan to try that first and then rebuild the carborator (with a genuine Mercury Kit) and chaeck all settings if the problem is not resolved. I change out the plugs and fuel filter every year, this spring included, so I am confident that is not the issue.