tri hull diving

[polecat77]

i have a 1976 chrysler 17ft tri hull with a 1987 evinrude 88 spl and it does good but when i get on plain she nose dive it had the finns on the foot i took them off have not had in water yet to see if thats my problem

 

[shrew]

Re: tri hull diving

Are you trimming the OB/Outdrive out at all once you're up on plane?

 

[southkogs]

Re: tri hull diving

Did it not do this in the past? Or has it been like this since you purchased it? Does it actually go into the water (submarine) or will it hold a nose down attitude while on plane?

 

[polecat77]

Re: tri hull diving

i only had the boat for 5 days. yes it holds the nose down while on plain at wot if i back it off to about 25mph its not as bad

 

[polecat77]

Re: tri hull diving

Are you trimming the OB/Outdrive out at all once you're up on plane?

i played with the trim no change

 

[Home Cookin']

Re: tri hull diving

trim's not working--not serious but can be expensive. Are you sure it's raising the motor under way and keeping it there? Old systems get soft. (nothing personal). Try sticking a board under it to hold it up.

transom's flexing in--serious

too much weight in the bow--if it's stuff or people, move it. If it's waterlogged, not good.

You're better off without the fins

I don't believe in adding weight to a boat to trim it, but for testing purposes, OK. Load up the stern and see what happens.

 

[polecat77]

Re: tri hull diving

transom is new trim is working i just took off the fins so i doint know if it will help yet

 

[acarter92]

Re: tri hull diving

This may not be a problem at all. It's normal for the bow to point up when getting on plane or when planning at slow speeds, but once on plane and up to speed the bow should go down and level the boat out.... Could it be that your just not used to this boat? Just a though...

Austin

 

[southkogs]

Re: tri hull diving

Those old Chrysler tri-hulls ran kinda' flat (not a lot of "bow up" attitude). Does it run the same with people up front or is it worse? I think I've seen your boat in another thread, it doesn't have a lot of freeboard at rest does it?

 

[polecat77]

Re: tri hull diving

not much freeboard i have not had anyone up front yet. when im up on plain is bounce side to side not up and down

 

[JimS123]

Re: tri hull diving

Common problem for an improperly installed fin.

If it still does it now, your motor is trimmed improperly.

 

[polecat77]

Re: tri hull diving

I'm going to go try it sat morning thanks

 

[ajgraz]

Re: tri hull diving

Where is the anti-ventilation plate in relation to the bottom of the hull? Should be even or maybe an inch or two higher. (Pics please)

If the leg is too far into the water (motor too low) it can cause drag that will both nose-dive you and cause that unstable side-to-side feel you mention when on plane.

People do try to fix that with a fin, but the best fix is to raise the motor on the transom.

 

[polecat77]

Re: tri hull diving

Where is the anti-ventilation plate in relation to the bottom of the hull? Should be even or maybe an inch or two higher. (Pics please)

If the leg is too far into the water (motor too low) it can cause drag that will both nose-dive you and cause that unstable side-to-side feel you mention when on plane.

People do try to fix that with a fin, but the best fix is to raise the motor on the transom.

its even with the bottom of the boat. when on plain the bottom of the fin is only thing in water

 

[dockwrecker]

Re: tri hull diving

You pulled off the stupid fin, that will probably take care of it. The trim will now take care of the rest.

 

[polecat77]

Re: tri hull diving

thank yall for all the info

 

[acarter92]

Re: tri hull diving

thank yall for all the info

So how did your test run go? What did you find out?

Austin

 

[polecat77]

Re: tri hull diving

We going test it out in morning

 

[polecat77]

Re: tri hull diving

we took it out and it did better still dives at wot we can cruze at 25 mph and it does good. them 88 spl like to drink gas

 

[steelespike]

Re: tri hull diving

The bottom may have a hook in it near the transom.Put a 3 foot straight edge on the bottom parallel with the keel. Your looking for a hollow spot between the straight edge and the boat.
If the transom is new the bottom may have been worked on and they didn't get it straight.
The 88 will use about 8-9 gph"gallons per hour"at wot.
Any motor will use fuel at about 10% of the hp. 8.8 gph for your boat
A number of things can waste fuel.Poorly timed or link n sync not set right. If there is a hole in the fuel pump diaphram.
If the bottom does have a hook it will likely use more fuel.