1987 Mercury XR2 will not take off unless trimmed up.

[Bubvicky]

The motor runs perfect on top end. All hoses were replaced, fuel pump replaced and checked good on dyno. It will not "power up" and get on plane until I trim motor up? Any ideas?

 

[alldodge]

My first guess would be your propped to high. Can you reach WOT RPM?

 

[QBhoy]

As Scott says above or a wild card might be to ask if you have vent plugs on the prop ? Have they fallen out ? Was it fine at any point ? Is this a new issue ? What kind of prop is it and on what boat ?

 

[Bubvicky]

This is on a 1987 16' Hydrasport. FYI... the foot has been change out and has an XR6 foot on it. There are no plugs in the prop. As far as WOT RPM... it doesn't - It just bogs down unless I trim it up.

 

[alldodge]

. As far as WOT RPM... it doesn't - It just bogs down unless I trim it up.

Sure sounds like your over propped or your motor is tired. Have you done a compression test, and what pitch prop is on it?

 

[Alumarine]

So even when you trim up it won't rev near maximum rev's?

 

[Bubvicky]

Heading to the water to test this afternoon. Will check on prop size. The mechanic said it tested good on compression. I will say that in neutral - it won't rev up to high.

 

[jimmbo]

An engine should NEVER be revved high in neutral. Well, unless you want to buy a new engine.

What else did the mechanic check or test?

 

[Bubvicky]

He said the compression was good (about 115 on all cylinders) and it "checked out" on the dyno. He replaced all of the carb hoses and the one to the tank. The prop is a 23. It looks like you can't plug the prop because they're not round.? Last weekend, I noticed that reverse doesn't have much power either. I didn't get to put it in the water today, will try tomorrow.

 

[Bubvicky]

Problem solved! Put a new 21 pitched prop that ran 5500-5600 rpms. Shot out of the hole almost like new. I guess I'm just surprised at how it went from being good last summer to now.? Thanks for the insight and advice!!

 

[1985 mercury]

How do you tell if a moter is locked up ? Been sitting for 3 years.

 

[alldodge]

How do you tell if a moter is locked up ? Been sitting for 3 years.

Howdy 1985

It's always best to start a new thread so you can get many more lookers at your question. But the short answer is if it will turn over. Post your question in a new thread listing the motor, year, what you know about it and what you have done