Mercury 2.5hp or 3.3hp 2Stroke

[coveman]

I am trying to find the difference in length of the leg of the std shaft and long shaft engines. I have a 2.5hp engine but not sure which it is? I understand a short shaft is normally 15 inches long compared to 20 inches for long shaft but where are the measurements taken??
The model no of my engine is described as 2.5 M which doesn't help much. Would M denote short shaft and ML be a long shaft ?? Any help gratefully received

 

[VicS]

I am trying to find the difference in length of the leg of the std shaft and long shaft engines. I have a 2.5hp engine but not sure which it is? I understand a short shaft is normally 15 inches long compared to 20 inches for long shaft but where are the measurements taken??
The model no of my engine is described as 2.5 M which doesn't help much. Would M denote short shaft and ML be a long shaft ?? Any help gratefully received

Measure from inside the clamp bracket where it sits on the transom top down to the AV plate above the prop.

A short/ standard shaft model will measure a bit more than 15". Probably 16" or so.
A long shaft model will be abit more than 20". About 21" or so.

M models are short shaft and ML are long shaft

There should be some guidance on shaft length in your owners manual, which can be downloaded from Brunswick Marine in EMEA Download Center - Download Center if you have mislaid your copy.
but there are several editions to choose from

 

[coveman]

Thanks Vic - great help.

The measurement from the clamp bracket to the AV plate is 17" and it is an "M" model so must be short shaft. I did look in my "Operation and Maintenance manual" but they do not refer to the different models - at least I couldn't find anything.

Thanks again

 

[coveman]

Well I did my usual service on the motor a 2.5hp Mercury 2 stroke made in 2000 - gear oil,plug, impeller check, greased propshaft, general lubrication. I put it away last autumn after a good flush with fresh water and stored in upright position so that it would drain well. Tell tale was working fine at the time
Tried it out in the wheely bin as usual last week - motor started first time on fresh mix but no water coming out of tell tale.
I tried my usual method of poking some guitar wire into the telltale outlet after taking off the rubber pipe - still nothing - this has usually cured it in the past.
Injected fresh water into the tell tale outlet and it flows out of the bottom of the engine but not through the impeller housing - I presume it is running out of an exhaust port?
Impeller looks in perfect condition as does its housing and was renewed last year.
Next tried compressed air both up into the exit from the impeller and down from tell tale hole - still nothing.
Thought it may be blocked channels in the head so tried undoing the four head bolts - three undid easily - but the fourth refuses to budge and I'm very wary of using too much force and shearing it off.
Thought I would try taking the leg off to see if the "up" tube was blocked but again one bolt undid easily and the other refuses to budge. Have tried dowsing the bolts in penetrant but so far it hasn't worked the bolts.
I also tried hot ( nearly boiling) water down the tell tale but again no help.

I've run out of ideas - I don't dare to try the bolts with any more force than I already have, so wondered if there were any more ideas - Vinegar? citric acid,Coca cola?????

I know its an old engine but it looks like new still so I'm loathe to give up on it.

 

[TSB240]

Well I did my usual service on the motor a 2.5hp Mercury 2 stroke made in 2000 - gear oil,plug, impeller check, greased propshaft, general lubrication. I put it away last autumn after a good flush with fresh water and stored in upright position so that it would drain well. Tell tale was working fine at the time
Tried it out in the wheely bin as usual last week - motor started first time on fresh mix but no water coming out of tell tale.
I tried my usual method of poking some guitar wire into the telltale outlet after taking off the rubber pipe - still nothing - this has usually cured it in the past.
Injected fresh water into the tell tale outlet and it flows out of the bottom of the engine but not through the impeller housing - I presume it is running out of an exhaust port?
Impeller looks in perfect condition as does its housing and was renewed last year.
Next tried compressed air both up into the exit from the impeller and down from tell tale hole - still nothing.
Thought it may be blocked channels in the head so tried undoing the four head bolts - three undid easily - but the fourth refuses to budge and I'm very wary of using too much force and shearing it off.
Thought I would try taking the leg off to see if the "up" tube was blocked but again one bolt undid easily and the other refuses to budge. Have tried dowsing the bolts in penetrant but so far it hasn't worked the bolts.
I also tried hot ( nearly boiling) water down the tell tale but again no help.

I've run out of ideas - I don't dare to try the bolts with any more force than I already have, so wondered if there were any more ideas - Vinegar? citric acid,Coca cola?????

I know its an old engine but it looks like new still so I'm loathe to give up on it.

Have you tried shocking the threads to help release any sticktion. Hitting the nut with a lump hammer and bolster. Dont do it too hard as the castings are fragile

 

[VicS]

Well I did my usual service on the motor a 2.5hp Mercury 2 stroke made in 2000 - gear oil,plug, impeller check, greased propshaft, general lubrication. I put it away last autumn after a good flush with fresh water and stored in upright position so that it would drain well. Tell tale was working fine at the time
Tried it out in the wheely bin as usual last week - motor started first time on fresh mix but no water coming out of tell tale.
I tried my usual method of poking some guitar wire into the telltale outlet after taking off the rubber pipe - still nothing - this has usually cured it in the past.
Injected fresh water into the tell tale outlet and it flows out of the bottom of the engine but not through the impeller housing - I presume it is running out of an exhaust port?
Impeller looks in perfect condition as does its housing and was renewed last year.
Next tried compressed air both up into the exit from the impeller and down from tell tale hole - still nothing.
Thought it may be blocked channels in the head so tried undoing the four head bolts - three undid easily - but the fourth refuses to budge and I'm very wary of using too much force and shearing it off.
Thought I would try taking the leg off to see if the "up" tube was blocked but again one bolt undid easily and the other refuses to budge. Have tried dowsing the bolts in penetrant but so far it hasn't worked the bolts.
I also tried hot ( nearly boiling) water down the tell tale but again no help.

I've run out of ideas - I don't dare to try the bolts with any more force than I already have, so wondered if there were any more ideas - Vinegar? citric acid,Coca cola?????

I know its an old engine but it looks like new still so I'm loathe to give up on it.

Maybe the water tube up from the water pump is blocked but more likely the channels between the top of the "leg" and the block

The parts diagram shows a flush plug ( #3), Have you tried taking that out and flushing from there ?

Heat, and gentle tapping with a decent sized hammer is the way forward with difficult bolts. To much force on a spanner is the sure way to wring the heads off.

 

[coveman]

Thanks Vic - I hadnt realised there was a flush plug - nothing mentioned in the handbook surprisingly! Ill give that a go - providing that bolt is not seized!!

 

[VicS]

Thanks Vic - I hadnt realised there was a flush plug - nothing mentioned in the handbook surprisingly! Ill give that a go - providing that bolt is not seized!!

This is what the manual I'm reading says

 

[coveman]

This is what the manual I'm reading says


View attachment 84225

Hi Vic,

Just realised my outboard is a 1999 model rather than 2000. Having said that the details you gave above from boats.net indicate a flushing plug on both year's models. However having checked mine there is definitely no plug and no mention of one in the mercury manual that came with the engine when I bought it new. The serial no of the engine is 0P022398 and the handbook 90-10100V80 697 9(1997) so all I can think is that mine predates the wash plug. Mention is made in the book to wash through in a tank however.

 

[coveman]

Vic,
I have some flushing tablets ( called Blue Thru) which are supposed to help clean out salt deposits, normally by flushing through with muffs or hose pipe. Obviously I cant do it this way, but I wondered if I was to lay the engine horizontally on the workbench with the leg slightly raised I could syringe this solution into the tell tail orifice and hopefully this would circulate around the cooling passages in the head if I left it to soak. Is there any disadvantage to doing this - presumably water cannot enter the cylinder or am I mistaken??

 

[coveman]

As a follow up which may help those with a similar problem on this engine ;-

Eventually after a few days of using penetrating oil on the 4th cylinder head bolt, and after starting the engine and letting it run for short time to heat the bolt up I managed to undo it by tightening then loosening several times. That allowed me to remove the cylinder head and I was surprised at how much salt deposit there was clogging the cooling channels seeing as I always flush with fresh water after each use. Part of it was completely blocked. I cleaned it as thoroughly as possible.
I then put it all back together and started the engine again in the wheely bin expecting to see a strong jet from the tell tale - but no - nothing but steam!
Back in the workshop, I decided to remove the leg to check for blockages in the up pipe. One bolt undid easily - the other sheared off. Luckily I was still able to remove the leg and then heat up the thread of the bolt and it came undone.
Using the airline, a blast up the pipe seem to loosen something and after replacing the leg and putting everything back together it went back in the wheely bin. This time there was a strong flow from the tell tale and all seems ok - Total cost 50p for the new bolt!
Patience paid off - it could have been very easy to shear the cylinder head bolts - they hadn't been undone for 20 yrs. Giving the bolts a coating of vaseline should help if they need removing again - I was told not to use mineral grease as this corrodes the alloy.