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1987 25hp Mariner, so hard to pull start

B

Beesaman

Contributing Member
Hi guys,
You have helped me in the past.
I have the above engine, but have not had the chance to use it yet, the bores were oiled for storage etc, just waiting for good weather.
I did start it to test run it, but Crikey it was hard to pull start,Felt like I was hitting a brick wall with the compression, is this a fact with this motor ?
I have only ever had an 8hp motor before this one, is there a knack to starting these, it did start second pull, but I found it hard to have one hand on the motor hood, as the manufacturer advises and pull the motor over with the other hand.
Help would be much appreciated .
 
I know what's wrong here and, if you're mechanically ambitious, you can fix it.

There's a hole drilled through the cylinder wall near the exhaust port. This is a compression relief. While cranking it lets enough air leak out to reduce compression and ease cranking. (During running the hole doesn't leak fast enough to matter.) That hole(s) is/ are plugged with carbon, but, if you remove the exhaust plate, you can drill the holes out and be good to go.

Jeff

PS: When doing a compression tests on motors with comression relief, you will get a lower reading that what's actually happening.
 
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Thanks fastJeff, good to hear that, I just could not understand it, pull the starter rope and bang it's so hard.
Do you think one of the cleaning products you spray through the air intake would help ?
Thank you
 
Hi Jeff,
I understand what you are saying.
I have looked at the motor, there are 11 bolts holding the exhaust plate, on looking, I can see 3 holes, I have taken a photo and would gladly email it to you and welcome your advice.
My Email is [email protected]
Many thanks
 
Do you have the cover off already? If so, look for a 1/4 or so hole just to the right of the exhaust port. That's the one.


Jeff
 
Be really careful removing those cover bolts or you'll snap them off. The best tool I've found to use is an impact wrench on its LOWEST setting; clank away until the bolt finally starts to turn.

Jeff
 
fastjeff said:
I know what's wrong here and, if you're mechanically ambitious, you can fix it.

There's a hole drilled through the cylinder wall near the exhaust port. This is a compression relief. While cranking it lets enough air leak out to reduce compression and ease cranking. (During running the hole doesn't leak fast enough to matter.) That hole(s) is/ are plugged with carbon, but, if you remove the exhaust plate, you can drill the holes out and be good to go.

Jeff

PS: When doing a compression tests on motors with comression relief, you will get a lower reading that what's actually happening.
Click to expand...
 
There is a 1/4 hole in the cylinders but these are for idling purposes. If these are stopped up it will not cause hard cranking just make a additional 10psi compression
 
racerone said:
Just remove exhaust cover and baffle plate.
Click to expand...
Ok. I have the exhaust plate off and i can see the hole but it doesn't appear to be blocked. I'm scared to drill the hole because I'm not sure how deep i can go. I have poked a wire in there and it appears to be touching solid metal about 1/4 of an inch deep.
 
Don't touch anything on your motor.----Hurry to a shop and have them explain what to do / inspect here.----Perhap look on E-bay for an electric start kit.
 
As stated in post #15 stopped up hole will not cause hard cranking...you have other problems such as seized gearcase or cylinder
 
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