Trim levels

ponchoman

Petty Officer 3rd Class
Joined
Aug 22, 2011
Messages
91
Is it normal for some boats (mine) to run full trim and not porpoise or cavatate? Seems I always needs full trim to maximize speed, while my buddies trim levels seem much lower. 1994 Glastron ssv 175 4.3 alpha w/4 blade 20 pitch alum. Maybe I shouldnt be comparing?
 

dazk14

Ensign
Joined
Jul 22, 2008
Messages
966
Re: Trim levels

All normal. 4 blades tend to reduce ventilation as compared with 3 blades.

4 blades tend to be stern lifting vs. bow lifting which can induce porpoising.

Is your trim limit switch adjusted properly...meaning your drive is angled up as far as your buddy's?

What are getting for GPS top speed and wot rpm?
 

ponchoman

Petty Officer 3rd Class
Joined
Aug 22, 2011
Messages
91
Re: Trim levels

Speedo is 42 mph, 4600 rpm. I'm gonna measure the trim rams and see if they need adjustment. I've had 3 blade on it before and it was 46mph @4800. Boat has always needed more trim than most others I've seen. I'm between half and 3/4 on the gauge.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Trim levels

I think a 4.3 In that relatively small boat should be running closer to 50 mph and possibly with up to a 23" prop.
Perhaps less for skiing or a heavy load.
Perhaps the hull has a hook near the transom?
Lay a straight edge along the bottom parallel with the keel near the transom should be no gaps.
 

ponchoman

Petty Officer 3rd Class
Joined
Aug 22, 2011
Messages
91
Re: Trim levels

I will check that, it seems to lay flat on the bunks but I guess thats not accurate enough. The trim rams were under measurement at full trim only 19.5" or so. I adjusted that to 20 3/4.
 
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