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Old 30 June 2010, 16:54   #11
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Country: UK - England
Town: iow
Boat name: kaykan
Make: tornado 5.8
Length: 5m +
Engine: Evinrude 115 HO
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Hi we have a 402 35hp merc that would run fine with muffs on it and run well in the water, but it would not pick up and get the rib on the plane ( sr4 ) . Problem in the end was the switch box only firing on one side, changed this and it has been as good as gold since
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Old 01 July 2010, 19:16   #12
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Country: Canada
Town: Ontario, Canada
Boat name: Sweet Thang
Length: 4m +
Engine: Outty
Join Date: Jun 2010
Posts: 10
Quote:
Originally Posted by 9D280 View Post
Firewall just killed last atempt at this post, so apologies if this is a bit disjointed


Anything will run on no load. All the firing cylinder is fighting against is a tiny amount of shaft bearing friction and compressing the air in the other cylinder(s)

My next thought for a "high level" test - pull the spark plugs out - is one of them substantially more oiled than the other? If so, clean & swap it to another cyl. Go for another run. Pull plugs again & see if the oiled one is the same cyl as last time if it followed the plug, replace the lot. if not, try the same test with the HT leads (Looks like yours are a similar type to mine - the crimped ends occasionally let go) Remember to check the Coil end as well. Repeat the swapping trick until you get the oiy cyl to move, then you have found the dodgy component.

Alternatively to check the HT side, if you have a spaky friend, ask him or her to megger your plugs & leads (insulation test). High frequency KV AC will break down insulatio nthat a conventional meter thinks is fine.

Another test could be to pull one plug lead off at a time & see if runs similar to when bogged. (not when it's running, obviously! )


Alternatively I managed to "re HT" my entire engine for about 30 in a local motor factors. A certain Shop with a big orange sign will double the cost of your engone just with the leads.......
Ok, I am now the fastest spark plug changer in Canada
So I pulled both plugs and the top plug was very oily and the bottom plug was like brand new (started test with two brand new plugs). I then rotated the two plugs and the top one is always oily and the bottm is nice and clean.

What do you mean by HT?

I checked the compression on the top cylinder and it holds about 94 to 100 PSI. I was not able to test the lower one, cause I didn't feel like taking the the bottom cover off to get my tester into the cylinder hole (besides I think the problem one is the upper one).

I also checked the spark on both wires and lots of spark on the two of them.
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Old 07 July 2010, 10:14   #13
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Country: UK - N Ireland
Town: Bangor, Co Down
Boat name: Ribeye & Tremlett 15
Make: Ribeye & Tremlett 15
Length: 4m +
Engine: Yamaha F40, Merc 500
Join Date: Jul 2010
Posts: 265
Hi, had a similar problem a few years back with my Merc 500, it was dirt in a high speed jet in a carb, have you cleaned the carb & jets and check the fuel tank, line etc for dirt/water in the fuel ?
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Old 07 July 2010, 13:03   #14
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Country: Canada
Town: Ontario, Canada
Boat name: Sweet Thang
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Update...

Okay, so on Thursday the wife and I decided to head up to the cottage for the long week-end. She asked as we left the driveway why I wasn't bringing the boat. Long story short she convinced me to bring the boat and I decided that I would try it at the cottage and if it didn't work that I would put a forsale sign on the boat at the cottage (may have been my frustration talking).
Soooo, got to the cottage, put the boat in the water, and the boat did exactly what it always does (no high RPMS), parked it at the dock, got a forsale sign stuck it to the side of the boat and it was done.... So I thought! First guy stopped and looked at the boat I told hime how much and the problem with the motor. Hewanted to try the boat eitherway, okay with me. We both jump in the boat I start the motor up and slowly putt away. The guy asked me to go WOT to hear the problem. Well guess what...... The eF'ing thing took off like a rocket like a child being chased with a wooden spoon
The boat was no longer forsale and ran like a charm all week-end, pulling skiers, tubes, went out for about 1 hour ride around the lake.

I did nothing to the motor since I rotated the spark plugs. The top spark plug is still oilier then the bottom.

Anyways thanks for all the comments and suggestions, however i guess she just had to be threatenedwith a little goodbye sign
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Old 13 July 2010, 09:33   #15
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
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Engine: Merc 60 Clamshell
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Quote:
Originally Posted by 2slow2go View Post
What do you mean by HT?
High Tension. AKA High voltage. It's the spark plug leads.

Apologies, I forget acronyms like that vary from place to place.
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