high rpm, little speed mariner 150

[BarflyRIB]

today we had a big trip planned, unfortunately I was just away and the engine did very weird - it's a mariner 150 '96 - when I throttle up, the rpms get up but no speed similar to this rpms, when I throttle back very slow the rpms goes down and suddenly the engine gets in gear and boosts up... it's like the propellor slips... when I did WOT, I was making speed but not the "G force" feeling you know... very very slow to higher speed...
I recently changed the spark plugs and it's another type than before...
anyone had the same problem? what could it be?

EDIT: getting it in back gear was also a problem...

[Downhilldai]

Sounds like you're spinning the prop bush

[BarflyRIB]

Originally Posted by Downhilldai

Sounds like you're spinning the prop bush

ok thanks, I will check the prop bushing - I remember it was like at a certain RPM level the prop gets his full grip and you could feel it (the boost :-) )

[jambo]

As you can see I have the same engine and had problems last year!! Have you checked your fuel system right through/ Eventually got my problem as a dodgy diaphragm!!
Hope this helps you get back on the water.

J

[9D280]

I had a similar thing on an old Johnson 25. Check round the hub of the prop - if you see a ring of "extruded" rubber (paint in that area wil lbe flaked off as well) , you're looking at a new prop. Basically if it's hit something, the bits of the rubber moulding (injected into place when the prop was made) break form their holes, and then you're just relying on the friction, which isn't enough, and so the hub starts to spin relative to the body, then of course the rubber starts to melt & it gets worse.......

[wavelength]

used to be a regular problem in the early days of thru prop exhausts even with relatively low hp models on the local fishing boats, but not seen much trouble with this for a long while-perhaps I've just been lucky eh. Trouble is you cant really feel any difference with the prop on the bench, just shows up in the way you say-the bush just lets go at certain loads. New prop methinks.

[Polwart]

Originally Posted by wavelength

New prop methinks.

can steel developments and the like no replace the bush?

[biffer]

Originally Posted by Polwart

can steel developments and the like no replace the bush?

yes

[chewy]

Originally Posted by Polwart

can steel developments and the like no replace the bush?

Thats if you can get a sensible answer from the lass on reception first.

[9D280]

Originally Posted by biffer

yes

Bearing in mind what they would have to do (clean out old bushing, line it all up, re- inject new rubber, then balance it all up again) I have to ask, assuming it's a standard off the shelf ally prop, would a replacement not be cheaper?

A nice stainless tuned to the rig one fair call to re- bush.