No power underload

Hi guys

while I am waiting for Arthur page to come out in a fortnight, anyone able to shed a bit of light on what is happening with my outboard.

I have a 2008 115hp Mercury optimax 2 stroke, and currently I have no power under load only goes at 6.5 knots, I have changed fuel tank replaced water separator filter, fuel filter new fuel hose and primer bulb put in 3 new spark plugs but still no power underload, perfect in driveway on the muffs but not on the water, I took prop off found a bit of line on shaft also pretty rusty behind prop (any thoughts there)I changed gear oil it was not milky it was dark oil but smelt burnt.  I thought it might have gone in guardian mode but I have no alarms or faults on my smart gauges any thoughts while I am waiting for Arthur.

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big john's picture

Posts: 8725

Date Joined: 20/07/06

Bush

Sun, 2022-02-06 09:54

Not sure on a motor that size, but I had a 15hp evinrude way back when that slipped the rubber bush in the prop due to overloading. As force built up with speed, the rubber bush would slip and it wouldn't go any faster even though the motor was revving as normal. 

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Marineboy's picture

Posts: 838

Date Joined: 14/03/14

Optimax

Sun, 2022-02-06 10:51

 Got a mate who had a similar issue with an optimax, it was the coils from memory. 

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Posts: 1084

Date Joined: 21/05/12

 Just Props  can check if it

Sun, 2022-02-06 11:16

the problem u describe, if the motor  is getting full revs i m unsure form your post - does it get full revs on water  - it can only be the gearbox or prop- if gearbox u would have no drive 

sounds like big john said - slipping bush in prop

it looks as if the grease in the bush has overheated- i ve seen simular on slipped bushes before

 

not the most expensive problem to have and an easy fix, takes like 5 mins

little johnny's picture

Posts: 5320

Date Joined: 04/12/11

Agree with first comment

Sun, 2022-02-06 18:47

If it revs out and doesn’t pick up speed.

scotto's picture

Posts: 2469

Date Joined: 21/04/08

injected?

Mon, 2022-02-07 12:29

is the motor injected, or carby?

 

I had a similar issue with my 4 stroke 140 suzuki. it struggled to get above certain revs, and I could only get 6-7 knots out of her. turns out the water seperator filter had a lot of water in it, and water made its way past the inline fuel filter, and into the high pressure fuel filter and high pressure fuel pump. these are the last stops before the injectors, and stopped the boat from going into high revs.

 

I had to disassemble the motor, manifolds, fuel lines, filters, etc and replace the HP fuel filter (which was only $100). I cleaned out the HP fuel pump whilst I was there, as its an absolute C**T to get back into later on. 

 

I reassembled everything, and got better performance out of her thane ever before!

sea-kem's picture

Posts: 14833

Date Joined: 30/11/09

 Mate had a similar issue

Mon, 2022-02-07 13:41

 Mate had a similar issue with his 30 Yammy 4 stroke with carbs. Plenty of revs with no load, soon as you put it into gear no power. Had a full rebuild of the carbs and it was a power house. 

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Posts: 694

Date Joined: 16/08/09

 I had a 90hp 2 stroke

Mon, 2022-02-07 14:29

 I had a 90hp 2 stroke mariner years ago that did exactly the same thing. Would only do it on the water under load. Was the coils. Cheap fix and can DIY 

little johnny's picture

Posts: 5320

Date Joined: 04/12/11

With rust on link

Mon, 2022-02-07 15:15

Doesn’t look like prop issue . Prob is coils ?. Need big bank balance when dealing with optimax . If you can figure out yourself way cheaper . Great motor in there day

surge's picture

Posts: 212

Date Joined: 17/08/09

 sound like same problem as

Mon, 2022-02-07 16:09

 sound like same problem as mine but i have 70 hp yammy , mine was a blocked jet. ran fine on the muffs under load would only get 8 knt

 

Posts: 218

Date Joined: 15/01/10

Overheating

Tue, 2022-02-08 08:30

 Is it overheating then going to limp mode?

Arthur Page will sort it either way.

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dakka's picture

Posts: 275

Date Joined: 05/03/06

 Yep problem was the coils on

Thu, 2022-02-24 21:53

 Yep problem was the coils on my outboard cheers

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"If we all fish for the future now there will be fish in the future"