Smart tabs cause overheating engine?

john from md · Jul 5, 2008

Strange question but I have to ask.

I have an '85 Bayliner Capri with an 85hp Force engine on it. It has never overheated when it was stock or when I used a Dole Fin. I decided to get Smart Tabs and mounted them as per instructions. They were set in the middle hole and are 40lb gas struts.

Today was the first time I got to put the boat through its paces as my trailer died and I just bought a new one. First off, the boat and engine are in excellent condition and, prior to this, I would get 40 mph at 5200 RPM. Today, I was only able to get 36.6 and, if left wide open, I got an overheat. If I throttle back it would stop. The other thing I noticed was that the boat seemed to have more hull in the water. I tried several engine trim positions but there was no change. I also noticed that, at high speed, the water level was even with the cav plate. Is this normal?

My next plan is to adjust the smart tabs to the lightest setting and try it. I won't be able to test it until next friday though.

Thanks in advance for any assistance.

John

I looked in the back of

QC · Jul 5, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

john from md said:
if left wide open, I got an overheat.

Seems odd, but a liitle extra load (tabs) may have pushed it over the edge. Seems that your cooling system would have to be very marginal though.

john from md said:
My next plan is to adjust the smart tabs to the lightest setting and try it.

Good plan.

john from md · Jul 5, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

Well it has a new pump and housing as of this year and has always pumped well. I put a tell tale on it and it pumps great at the lower speeds but doesn't go as far at full throttle. That is what prompted me to look at the water level at the cav plate. I would think that if I was planing properly, the rear end of the boat would be down further. As it was, at 30 mph, i leaned over the front of the boat and it looked like 3/4's of it was still in the water. The boat was loaded light with only me and a friend and no gear.

John

fishmen111 · Jul 5, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

Are you still running the fin, and if so, was it out of the water during your high speed run? Get it off of there if not. If I understand your description of your cavitation plate depth, the two devices may be working against each other.

wca_tim · Jul 6, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

I've noticed that if I have the bow pushed down with tabs and the drive trimmed out a bit (doing at lower speeds playing with pulling boarders...), the water flow isn't as good through the engine and it runs a little hotter.

Sounds like you're getting too much stern lift with the tabs and driving the bow down and stern up... would bet that much more if you've got the fin on too...

take the fin off and go with your plan to adjust the tabs... bet it will improve. Also, trim in a little when you see the temp go up and see what happens..

john from md · Jul 6, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

I removed the Doel Fins before I installed the Smart tabs. The Smart tabs are not controllable from the helm, they use gas charged struts and adjust automatically with water pressure.

I think that the struts may be too stiff for my boat and I may have to change them out for lighter ones.

John

tashasdaddy · Jul 6, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

"I also noticed that, at high speed, the water level was even with the cav plate. Is this normal?" that is what you want. where was the water pump last serviced, i'm think it is just coincidence. i think you have a water pump going.

marine4003 · Jul 6, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

You got a coupla' things going on here...Smart tabs bringing down the bow=more hull in water=motor working harder=overheat, Then i dont know how long you run it WOT,But any lenght of time is bad,for short periods fine,but 5 min up prolonged..not good.due to the light weight of that boat,try tabs at lightest,and remove the dole fin.

john from md · Jul 6, 2008

Re: Trim tabs cause overheating engine?

Re: Trim tabs cause overheating engine?

Water pump was replaced two months ago by me. No problem with overheating before adding the Smart tabs.

The dole fins have been removed from the start and the boat has not been run with fins and tabs.

When I had the dole fins, I never had a problem planing or overheating.

I have adjusted the smart tabs to hole number 1 and will test it on Friday.

John

DeepV · Jul 6, 2008

Re: Smart tabs cause overheating engine?

Are the tabs lifting the stern so high you are having trouble ingesting water?

If the tabs are easy to remove I would try again and see if it overheats.

Outsider · Jul 6, 2008

Re: Smart tabs cause overheating engine?

When I had the dole fins, I never had a problem planing or overheating.

And you went to tabs because ... ?

john from md · Jul 6, 2008

Re: Smart tabs cause overheating engine?

I switched to the tabs because we don't ski anymore and the smart tabs,(on friends similar boats) seemed to give a more stabiler ride in the bay.

John

Hitech · Jul 6, 2008

Re: Smart tabs cause overheating engine?

john from md said:
...prior to this, I would get 40 mph at 5200 RPM. Today, I was only able to get 36.6...

That means they are to stiff. Move the strut on the tab itself closer to the transom (more leverage, less pressure position). You need to GAIN a MPH or 2 or they are too stiff. I think your overheating problem will go away once the tabs are adjusted properly.

wca_tim · Jul 6, 2008

Re: Smart tabs cause overheating engine?

Got you on fin gone and have smart tabs on my boat. I switched types last week and found that the newer ones, which have a little different shape and surface area placement, push the noze down a good bit more than the first ones. I remounted mine to solve the problem, but surely you should be able to adjust the positioning of the lower end of the shock as explained above and worst case perhaps to move the upper bracket on the transom up just a little to get a little different angle.

How far above the bottom of the boat is the bottom of the leading edge of your tabs? Do you have a picture?

The post above mentioning water pickup is exactly what i was referring to and it was hapennong on my boat with the new tabs when i would trim it out... the combination of the water inlet angle and the stern being up in the water was enough to do it.

Hope this is helpful

john from md · Jul 7, 2008

Re: Smart tabs cause overheating engine?

Tim,

I have the Smart Tab SX and mounted them per the instructions. They said mount the bracket flush with the bottom of the boat. When you install the tab, it hangs at a predetermined position as it has a molded in stop. On Friday, I will try them out with the tabs in the #1 hole. I will report on what happens.

I have the SX 40's which I thought were the correct model for my boat. The boat is a '85 Bayliner Capri with an 85hp Force engine on it. I must admit, the guide on the Nauticus website was not the easiest to interpret. I wonder if the 40's are too strong for my boat?

John

Hitech · Jul 7, 2008

Re: Smart tabs cause overheating engine?

I have the 60s on my boat. There was a HUGE difference between the middle hole and the hole closest to the transom. The middle hole was too much lift for me. The prop would ?blow out? if I tried to accelerate very fast, even fully loaded (4 adults). I also lost a lot of WOT MPH. When I adjusted them to the hole closest to the transom no more prop ?blow out?, even with just me in the boat. And the WOT MPH where back to normal. I doubt that the 40s are too much. I think you will find that adjusting them will make a big difference.

john from md · Jul 7, 2008

Re: Smart tabs cause overheating engine?

Hitech,

Thanks for sharing that info. I plan to use the lightest hole as almost the whole boat was in the water with the middle hole. I was pretty impressed that the engine could still give me alot of power even with all that drag.

John

Hitech · Jul 7, 2008

Re: Smart tabs cause overheating engine?

No Problem. Also, the bow was far enough down that I almost couldn't turn the boat, severe bow steer.

Once adjusted they are great. With just me in the boat I could time how long it took to get on plane as it just seemed to start there!

azlakes · Nov 21, 2008

Re: Smart tabs cause overheating engine?

john from md said:
Hitech,

Thanks for sharing that info. I plan to use the lightest hole as almost the whole boat was in the water with the middle hole. I was pretty impressed that the engine could still give me alot of power even with all that drag.

John

So John,

how'd that adjustment turnout? I'll soon be mounting those same brand tabs. Your over heating and WOT resolve itself with the change in position?

Thanks

mickjetblue · Nov 22, 2008

Re: Smart tabs cause overheating engine?

John,

What is the length of your Capri, 19'? I have an '85 Capri 1950, and I have
to admit, I was not comfortable with it in the bay when swells were rolling.
I can understand wanting more stability, but I don't think I would want the bow
angle down any more than what it's at with optimum planing. Running an i/o,
but probably same boat.

I'd like to know how things work out with your tabs.

Smart tabs cause overheating engine?

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