Trim Question

[JoeCrow]

I have a 1986 Bayliner 19' cuddy with a 125 Force
I believe it is a 25" shaft
My cavitation plate is about 5" above the keel
Is the shaft too short?
I've attached some pix of the motor on the boat in the down position
I can trim it lower (and do when running the boat)
Question is,
Could this cause it to overheat ONLY at WOT?

 

[GrindKore]

Re: Trim Question

The position of motor relative to hull should not affect engine cooling as long as the prop and water intake remains submerged. However, when you go WOT and boat lifts up your water intake may be picking up air bubbles since at that point it would be fairly close to the surface.

 

[JoeCrow]

Re: Trim Question

That's what I'm thinking,
I've exhausted every other possibility
and it only overheats at WOT and as soon as I bring it back,
the alarm silences
The water intake seems to be 2" below the keel and I was wondering if that's normal
Thanks,
Joe

 

[maxum247]

Re: Trim Question

The anti-cavatation plate needs to be level with the bottom of the boat. With the water pickup's 2 inches below the bottom of the boat it's going to get air and overheat due to lack of water circulating thru the engine. Not familar with the transom height on the boat you have but it sounds like your running a short shaft engine on a long shaft transom. Measure the height of your boat transom from the point where the engine sits on the transom to the bottom of the keel, 20 inches is a short shaft transom and 25 inches is a longshaft transom! I wouldn't continue to run it the way it is! max!

 

[jerryjerry05]

Re: Trim Question

Yup too short for what you have.It will overheat at speed.If you want to keep that motor you might be able to cut down the transom. Post a couple of pics showing the upper transom. Force didn't make a longer motor. There area lot of used motors out there.Just look for a 30" shaft.Buy EFI/DFI if your gonna change.Might as well save some gas money.Merc seems to get the best economy.Jerry

 

[RRitt]

Re: Trim Question

i'd like to ask the obvious ...

how long have you had this boat? did it always overheat? If you have owned the boat long time and it just started overheating then i think it's probably your impeller, water-tube, or engine cooling passageways.

 

[JoeCrow]

Re: Trim Question

Pix of the boat, transom and motor are in my first post
From what I can tell, the motor and transom are both 25"
The "torpedo" where the water intakes are,
are about 4" below the keel
The anti-cavitation plate is about 4" above the keel
It's either a poor design or I need an XL 30" shaft
I had the boat since last year
It always had overheating issues,
but they seem to have gotten a lot worse recently
New impeller, pump housing, t-stat and spring all new in the last month
I've seen this problem mentioned a lot on various boards,
with the same boat/motor combination
There doesn't seem to be enough "meat" there to cut the transom down
I think it would swamp with any backwash if it were lower
I guess it's time for a new motor
I'm looking into a new Optimax 115
Pricey, but maybe worth it in the long run
Thanks,
Joe