Boat Trim/Speed

6/1/18 @ 2:54 PM
ORIGINAL POST
Jared
Jared
MEMBER since 7/22/01

I was out in my boat last week on bago.

17ft Starcraft Alum deep V. I recently added an 8hp kicker (4 stroke). I lost about 5mph, I thought that was quite a bit, at least more than I expected. The boat has an '04 115hp 4-stroke. I got about 40mph out of it before the kicker.

Wednesday I was up north, it started to rain. Put everything away and go. Full throttle, 7.5mph. Obviously somethings wrong...

It won't trim up or hold trim under power. I trimmed it up and as soon as I hit the throttle, the motor came back down to the transom. It trims up/down fine when not under power.

I haven't really looked at it yet, but any chance it's just low on oil? Leaky seal or such? I know those trim units aren't cheap.

Any ideas or suggestions are appreciated. Thank you.

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6/16/18 @ 11:03 AM
Jared
Jared
MEMBER since 7/22/01

Thanks for the info swede.

Definitely something up with the big motor. 

Had two other guys out with me this morning and dropped from 30mph to 28ish, which is to be expected.

I'm thinking it's on three cylinders.

Will have to check to check spark, gas and compression.

Anything else I am missing?

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6/15/18 @ 10:17 AM
PimplySwede
PimplySwede
USER since 1/6/09

The red ring should be on the bottom.  If it is floating, that means there is water in the fuel.  It sinks in gas, floats on water.

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6/15/18 @ 9:44 AM
PimplySwede
PimplySwede
USER since 1/6/09

Jared - found this discussion on another boating forum - answers a lot of your question about speed/RPMs.

https://www.thehulltruth.com/boating-forum/309951-why-does-load-affect-rpm.html



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6/15/18 @ 8:57 AM
Jared
Jared
MEMBER since 7/22/01

I think what I used was Merc "powertune" IIRC.

It actually cleared up all the issues after having at the dealer and a $500 charge with no fix. This was years ago.

On  the back of the motor (inside) there is a "sight glass" with fuel in it that has a red ring in it to indicate if there is water in the gas. I have no idea what it's called.

Is that red ring supposed to be floating or at the bottom? I can't remember and I can't find anything in the manual.

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6/14/18 @ 10:33 PM
hntesox
hntesox
USER since 1/11/02

I run “mercury quickleen #2” every tank. It’s designed for outboards and HELPS stabilize and keep carbon off piston tops. Similar to sea foam (which I also run in other motors) but IMO I’d rather use what is recommended. 

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6/14/18 @ 7:12 PM
Jared
Jared
MEMBER since 7/22/01

PS,

I was thinking along the same lines. I don't want to do it, but need to eliminate all possibilities. 

I should probably get a compression gauge just to double check as well.

Fun, fun, fun.

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6/14/18 @ 8:54 AM
PimplySwede
PimplySwede
USER since 1/6/09

I just don't know enough about motors to suggest anything other than the obvious.

Just can't really believe that adding 80 pounds would slow you down that much in a 17' boat with a 115 4-stroke.

Really the only way to test that theory would be to take the kicker back off......PITA, but cheaper than taking the boat to a mechanic and saying "Figure it out for me."

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6/13/18 @ 2:26 PM
Jared
Jared
MEMBER since 7/22/01

Plugs are new, gas should  be fine add seafoam to every tank and run premium.

Anyone know the name of that mecury EFI cleaner?  I seem to think it's like a foam.

Had water in the gas years ago and that cleared it up. It'd be worth a shot.

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6/13/18 @ 11:56 AM
PimplySwede
PimplySwede
USER since 1/6/09

Last year's gas?  Bad spark plug?


Regarding trimming while in motion - I have a 3.0 Mercruiser I/O in my Northwood 191 - they told me never try a hole shot with the motor trimmed up at all because of too much torque.  Once I'm up on plane I can adjust it.

Edited on 6/13/18 11:59 AM
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6/12/18 @ 2:18 PM
Jared
Jared
MEMBER since 7/22/01

Well the prop was loose. Rattling back and forth. Re-Torqued and still only get 30mph and 4800 RPM's.

Previously got 40mph and 6100 RPM's, right below the line which is 6200 if I remember correctly.

Trim seems to be working fine as of right now. I did check the oil, but the boat wasn't level. I leveled the boat and added some oil.

RC, my manual doesn't say anything about trimming under power. That's basically what it's for, right?

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Displaying 1 to 10 of 28 Posts