Mariner 90 HP requires slow throttle for movement

[Jumpinjon]

I'm very new to boating and to boat motors but here's my deal. I've had this '94 Pro Craft Bass boat with a 90 HP Mariner for a year now and it was working fine last winter before I winterized it by fogging the engine. The first time I got it out after its winter rest and ever since, I cannot "punch" to full throttle and get the boat on plane. My RPM spikes into the 7000 range and I go nowhere. If I slowly increase the throttle though, my speed slowly increases and I can eventually get on plane. What would cause this. I removed the prop and couldn't find anything that would cause it to slip. I did remove some fishing line that was wrapped around the shaft. Would that cause it? Any suggestions before I take it to a pro?

 

[Trent]

Re: Mariner 90 HP requires slow throttle for movement

Get a marker. Mark across the prop hub. Go boating. Raise the engine and see if the mark no longer lines up. If so you have a spun prop hub. A prop shop can press a new one in for you or you can buy a new prop.

 

[Chris1956]

Re: Mariner 90 HP requires slow throttle for movement

Jumpinjon, I suspect your carbs are incorrectly adjusted or clogged. Try opening them up(CCW) 1/8 turn each. The carbs do not have accelerator pumps, and therefore rely on a rich idle mixture to accelerate quickly. The downside of the rich mix is the idle performance is poor. If the motor accelerates quicker after the carbs are opened up the 1/8 turn (counterclockwise), and the idle performance is OK, you have fixed it. If one or the other is poor, the carbs need to be cleaned.

 

[2springers26]

Re: Mariner 90 HP requires slow throttle for movement

sounds like your prop hub spun..... Try another prop

 

[Merc90HPnewbie]

Re: Mariner 90 HP requires slow throttle for movement

Same thing happened to me last year, I was told spun hubs 'just happen' like flat tires. And you won't be able to spin it by hand, it will look normal. My symptoms exactly the same as yours, try to throttle up and RPMs run away. If you nudge it up you can get maybe 1500 rpm out of it.<br />If it's a good prop you can get a new hub pressed in. If not, go for a new prop. Remove that fishing line, it can wreck the seals and let water in where there shouldn't be any.