Porposing, trim tabs?

[TTKarl]

Wow I really can't spell. Anyways I've got a question. My boat porposes or bounces up and down quite a bit in the water. It's a cen grey thunder. I can adjust the trim on the outdrive to correct some of it. I am wanting to go to a solid shaft and get rid of the steerable outdrive. What can I then do to keep the boat flat on the water and not jumping up and down? It gets so bad at some times it overheats because the pickup won't stay in the water long enough.

[Ron Olson]

Karl, I haven't had any trouble with mine porpoising. I have mine a little nose-heavy with a larger fuel tank and smaller battery pack.

[TTKarl]

Your using a sullivan right? How big did you say?

[Ron Olson]

You're gonna make me look again aren't you. Be right back.













OK, I'm back. It's a Sullivan SS-4.

[haljmac]

put a straight edge on the bottom of the hull, to check and make sure that there not any dips. Also you may have the strut set with to much positive. I would do these things before putting trim tabs.

[TTKarl]

Well went to the pond today to try to figure this out. I can adjust the strut up not sure positive or negative. Basically it's so the prop points straighter instead of down I thought this would make it worse but it made it better I think it must have been trying to push the bow down too far then bouncing back.

But wait there's more :) I feel like an infomercial. Now after about 1 full throttle lap i pull it in and steem is puffing out of the water outlet, Run around a little and it turns back into water. When I go by at full throttle I see no water coming out of the pickup. I had this same problem when I tried to use a 42mm graupner prop. Do you think I install a pickup on the hull instead of on the rudder?

[Ron Olson]

What might be happening is that the larger prop is putting more of a load on the engine, leaning it out thus making it run hotter. The problem with mine is that I put on an Octura water outlet to neaten it up. It fits into the stock outlet hole with no mods but as you know it comes out on the starboard side. I run mine in a clockwise oval just like my other boats and it makes it difficult to see the water coming out at speed. You can try the transom mounted water pickup but first see if there is anything in the cooling system that is blocking the flow of water. It doesn't take much to clog it up.

[haljmac]

If you want to fix it so that you can really see if you are geting water through the engine. Remove the hose fitting on the exit side of the cooling head and plug it, then just above wher the plug you put, drill a 1/16" hole on the top of your cooling head to let the water out. When running you will see the water shooting into the air. from even across the pond.

[TTKarl]

I really hope your just kidding. Drilling into the head makes me kringe. I've checked for a clog I can blow through it I dunno if I should pull the head apart and clean it or what but It seems to be ok.

I know they make water pumps for the gas motors is there such a thing for a boat this size?

[Ron Olson]

There is not a water pump made for a small boat that I know of. If there was, it would be large and bulky, adding more weight to your boat.
Haljmac, the water exit that you are talking about would work except for one thing, the boat has a cowling that completely covers all of the running gear and radio system. all that it would do in this boat would be to fill it up eith water, something that this boat doesn't need because of the exposed radio equipment, a downfall of it's design.
If you want to make your own water pickup, use a piece of 1/8" brass or aluminum tubing and attach it to a similar plate to attach to the transom. Cut it at a 45 degree angle and place it so that it barely sticks out under the hull.

[haljmac]

Ron is right you don't want the water in the hull, sorry I did not know that you was running with a cowling. The brass pick up tube works good. If you can blow through it with no problem then your ok. (that is through all of the cooling system) If you are getting stem, kinda sounds like you are running too lean.

[TTKarl]

Ok, when I attach it to the transom I probally use screws. Do I need to use any kind of sealer around them? I know that most of the tubes that you attach hoses to have a flare at the end to help keep the hose on. Is there a tool that makes these flares like in auto brake lines?

[Ron Olson]

A little sealer never hurts on boats around anything. you really don't need to flare the fitting much, use a phillips screwdriver to work it out. If you want to go further, get some fuel line barbs from Du-Bro and solder it on.

[TTKarl]

Ok, I made my own water pick-up and tested it out. Wow what a differnce the water shoots 8 in out the side of the boat. Tried it with the 42mm prop and with the outdrive all the way up. Perfect no porposing, no steam. Thanks for all your help guys.

It never fails though the universal at the back of the boat is broken now. Seems with the outdrive all the way up it doesn't want to stay together. Got water in the servos too. I guess that's what makes it fun though. By next year this time this thing should be bullet proof though.