Removing powerhead from 4hp 2T Mariner

[weustace]

I've had a long-running saga with my antiquated 4hp (2T) Mariner. Despite its extreme simplicity, it fairly abruptly died on me on passage a while ago; it has since been lavished with some £200+ of "professional" attention with no substantial improvement. Both I and the mechanic have cleaned the carb extensively; he also identified and replaced a damaged fuel pump membrane. The symptoms are interesting: it starts and runs fine, though sounding a little husky (recording could be supplied if residents of this forum possess outboard-whispering skills), but dies as soon as power is demanded. Compression seems broadly OK - I measured it at 80psi or so at the time of the failure last year as against 90-100ish for the fully working outboard, and given the cheap instrument I am using I think this difference may be within the error bounds of the measurement. I prompted the mechanic who fiddled with it to check this, but he never reported back his findings - though he did say he'd try it.

Thoughts based on the above are welcome. The outboard is a 1997 model badged as being made in Belgium.

The more direct question: I have decided to take the powerhead apart and try giving it all a good clean. Even if this fails to deliver a performance improvement, I hope it might be educational... So far, I have removed the six bolts penetrating the powerhead assembly from under the cowl (photo attached with them partially reinserted to avoid loss), but don't seem able to remove the assembly. Is it just a matter of more force for the (doubtless corroded) joint, or am I missing something? Shop manual is next on the purchase list!

Regards
William

 

[jamie N]

Wait for the manual. You won't be sorry.

 

[Boathook]

If it has forward, reverse and neutral gears you will possibly have to separate the gear linkage in the leg. Another item holding it all together could be the drive shaft. Normally a spline fit but if not recently separated possibly stuck together.

I would wait for a manual or see whether you can find a 'parts' diagram 'online'.

 

[fisherman]

TBH I don't know that removing the head will get you anywhere. The only reason I had to was for a seized gear change lever. All the fuel/spark stuff is available to you without breaking it apart.

If you hold the tank up higher than the engine does it run? Or keep squeezing the bulb? If so it's fuel delivery.

 

[VicS]

I've had a long-running saga with my antiquated 4hp (2T) Mariner. Despite its extreme simplicity, it fairly abruptly died on me on passage a while ago; it has since been lavished with some £200+ of "professional" attention with no substantial improvement. Both I and the mechanic have cleaned the carb extensively; he also identified and replaced a damaged fuel pump membrane. The symptoms are interesting: it starts and runs fine, though sounding a little husky (recording could be supplied if residents of this forum possess outboard-whispering skills), but dies as soon as power is demanded. Compression seems broadly OK - I measured it at 80psi or so at the time of the failure last year as against 90-100ish for the fully working outboard, and given the cheap instrument I am using I think this difference may be within the error bounds of the measurement. I prompted the mechanic who fiddled with it to check this, but he never reported back his findings - though he did say he'd try it.

Thoughts based on the above are welcome. The outboard is a 1997 model badged as being made in Belgium.

The more direct question: I have decided to take the powerhead apart and try giving it all a good clean. Even if this fails to deliver a performance improvement, I hope it might be educational... So far, I have removed the six bolts penetrating the powerhead assembly from under the cowl (photo attached with them partially reinserted to avoid loss), but don't seem able to remove the assembly. Is it just a matter of more force for the (doubtless corroded) joint, or am I missing something? Shop manual is next on the purchase list!

Regards
William

I'm not sure why you want to remove the power head
It may just be stuck by the gasket or the drive shaft may be rusted into the crankshaft

I'd probably take the lower unit ( gear case) off first... that should pull the drive shaft out from the crankshaft provided its not rusted in and allow some scope for rocking the power head to free it from the gasket

At 80 psi the compression should be OK
Have you checked the strength of the spark. It should be strong enough to jump a gap of about 3/8" in a adjustable gap spark tester

 

[chris-s]

We had a similar mariner 4hp 2s that I could not get to run right at all, so somewhat reluctantly took it to the ‘outboard guy’, he knew instantly what it was, the crank seal leaking air into the case. Of course to fix it you have to remove the power head…so whilst you have it off, that might be something you could look at.

 

[dawnchorus]

I've had a long-running saga with my antiquated 4hp (2T) Mariner. Despite its extreme simplicity, it fairly abruptly died on me on passage a while ago; it has since been lavished with some £200+ of "professional" attention with no substantial improvement. Both I and the mechanic have cleaned the carb extensively; he also identified and replaced a damaged fuel pump membrane. The symptoms are interesting: it starts and runs fine, though sounding a little husky (recording could be supplied if residents of this forum possess outboard-whispering skills), but dies as soon as power is demanded. Compression seems broadly OK - I measured it at 80psi or so at the time of the failure last year as against 90-100ish for the fully working outboard, and given the cheap instrument I am using I think this difference may be within the error bounds of the measurement. I prompted the mechanic who fiddled with it to check this, but he never reported back his findings - though he did say he'd try it.

Thoughts based on the above are welcome. The outboard is a 1997 model badged as being made in Belgium.

The more direct question: I have decided to take the powerhead apart and try giving it all a good clean. Even if this fails to deliver a performance improvement, I hope it might be educational... So far, I have removed the six bolts penetrating the powerhead assembly from under the cowl (photo attached with them partially reinserted to avoid loss), but don't seem able to remove the assembly. Is it just a matter of more force for the (doubtless corroded) joint, or am I missing something? Shop manual is next on the purchase list!

Regards
William

Hi William,
I am running into a similar issue with my Tohatsu 4hp. I need to remove the powerhead but after removing the 6 bolts from the midsection, the powerhead won't budge at all.
Were you able to get yours off in the end?
Thanks,
David

 

[weustace]

Hi David

Apologies for this - meant to reply and never did. Equally, I never made a serious attempt at removing the powerhead: I bought a copy of the shop manual, which is worth seeing, but it makes this operation look quite complicated to put it mildly. I was planning to take it to a different mechanic to be looked at but have yet to get round to it.

Regards
William

 

[dawnchorus]

Hi William,

Funny coincidence - I am currently working on it and just managed to get the powerhead separated from the midsection at the exact time you replied! What I did was to put the 6 bolts back in the bottom and use a drift punch with a hammer to try to loosen up the powerhead. That didn't solve it, so I started hitting the back of the powerhead with a rubber mallet (mostly out of frustration) but it worked and the powerhead came loose! I saw a lot of corrosion between the gasket so that might be what caused the issue.

Hope this helps you when you get back to it. I also have been working on this for over a year and almost gave up.