Trim right or wrong

[jallen100]

So I am getting conflicting stories on how to trim my boat. Let me first start by saying that I had a 17 prop on my boat but it was hitting around 5600 RPM WOT trimmed all the way down. So i put a 19 on it and now it seems like a turd when taking off and seems to take a while to get up to speed. It is not very reactive to the new prop but the top end RPMs are around 4800 - 5k now. I was also getting around 38-40MPH with the 17 and now about 34-36MPH with the 19. I pretty much do everything trimmed all the way down. Is there something different that I can do to help get up out of the water a little faster? I have a 21.5 Thompson cuddy with a 4.3 mercruiser.

 

[NYBo]

Re: Trim right or wrong

You shouldn't drop that many RPMs at WOT with a 2" increase in pitch. Methinks your motor isn't running up to snuff.

 

[rallyart]

Re: Trim right or wrong

I'd get the actual pitch checked on the two props. I've seen 19s that were actually 22.

 

[jallen100]

Re: Trim right or wrong

I have been fighting an intermittant stalling issue which I posted about as well which may be contributing to this. I probably should put a set of plugs in it but I have no idea how I am going to get to them. I cant even see them.

 

[dingbat]

Re: Trim right or wrong

The only time you should be trimmed all the way down is at take off, if that. On plane the prop should be running parallel to the surface of the water.

Once on plane, keep trimming up until you reach max. rpm w/o ventilating

 

[sbooy42]

Re: Trim right or wrong

The only time you should be trimmed all the way down is at take off, if that. On plane the prop should be running parallel to the surface of the water.

Once on plane, keep trimming up until you reach max. rpm w/o ventilating

agree...

 

[ziggy]

Re: Trim right or wrong

^^^, yep, agreed here too...

check this out.. http://www.boattest.com/Resources/view_news.aspx?NewsID=3348 or google how to trim your boat...

 

[steelespike]

Re: Trim right or wrong

I think you need to verify your tach is accurate.
Usually you would only run trimmed down for hole shot or to try to stay on plane an reduced speed.perhaps a heavy load.Once planed you should trim up to the ideal speed and rpm.
But first verify your tach; possibly borrow a shop tach or have a tech check your rpm.

 

[DuckHunterJon]

Re: Trim right or wrong

Yup, next time you go out, trim down, floor it, when you hit your top speed you noted above, start trimming up. I think you will be surprised how much extra speed you see.

 

[jallen100]

Re: Trim right or wrong

I did have the tach checked about 3 weeks ago when they installed the new prop. Now that I know I have been trimming it incorrectly, I am sure I will see a difference. Thanks for all the help guys. What is ventilating?

 

[FlyinGuy1017]

Re: Trim right or wrong

'Ventilating' or 'cavitation' is where the prop is spinning air instead of water. You'll know it if the boat looses thrust, and the motor sounds like it doesn't have a prop attached. Typically happens when your trim is up too far and during hard corners.

One option you have to help with your hole shot is to install a hydrofoil or 'whale tail' on the outdrive. It'll get the boat up on plane faster, and sometimes give a slightly higher economy and top end.

Good luck!

 

[dockwrecker]

Re: Trim right or wrong

One option you have to help with your hole shot is to install a hydrofoil or 'whale tail' on the outdrive. It'll get the boat up on plane faster, and sometimes give a slightly higher economy and top end.

Good luck!

Yeah, good luck. Fins create more problems than they solve.

If after becoming more familiar with the trim angle that your boat wants to run at and you still need additional stability or help out of the hole, the next step is a tab system. For a novice boater or a light craft, go Smart Tabs from Nauticus. Mount them as far outboard on the transom as possible, that's where the lift and stability come from that a fin can never accomplish. Think of it as walking on snowshoes vs. high heels over thin ice. The weight and drive force needs to be distributed across the transom as wide as possible for maximum lift and axial stability.

 

[jallen100]

Re: Trim right or wrong

'Ventilating' or 'cavitation' is where the prop is spinning air instead of water. You'll know it if the boat looses thrust, and the motor sounds like it doesn't have a prop attached. Typically happens when your trim is up too far and during hard corners.

One option you have to help with your hole shot is to install a hydrofoil or 'whale tail' on the outdrive. It'll get the boat up on plane faster, and sometimes give a slightly higher economy and top end.

Good luck!

It actually already has a hydofoiol installed. It was there when I bought the boat.

 

[DuckHunterJon]

Re: Trim right or wrong

Take the foil off and re-do your testing (trimming properly). You may very well find it performs better with out it. If not, it's easy to swap back on.

 

[jallen100]

Re: Trim right or wrong

Take the foil off and re-do your testing (trimming properly). You may very well find it performs better with out it. If not, it's easy to swap back on.

I will try that out