25" Shaft Motor mounting w/ Jack Plate

[-dirt-]

Hi all,

I just got my new-to-me cheap-find pontoon. Its a 1993 24' Grumman. I am picking up a motor this weekend. Its a 25" shaft (extra long) Honda 150 VTec. The transom is about 18" tall (from top to bottom; has the open, drain-style pod). Also it is approx. 27-28" from the top of the transom to the bottom of the toons. This barge has 24" pontoons.

I believe this barge is meant for a 20" shaft motor. Not sure.

I plan to add a 3rd toon and can integrate a taller transom on it, plus it will probably ride a bit higher out of the water with the extra flotation. But in the mean time, I need to use the pontoon prior to adding the 3rd toon and need your input on mounting this engine.

So...I plan to mount the jack plate (Bob's 4" HD) directly to the existing bolt holes in the transom. The jack has a 1 1/2" built in rise. It adjusts up to 6" high for a total of 7 1/2" above the transom. Should I mount the engine on its lowest setting on the jack plate? I think so, but want y'alls input. I don't want to have my motor too deep all the time and getting that drag, with my only option being to trim it up.

(I also need a recommendation for a prop, but I can start a new thread, if thats preferred. Should it be here or in the "props" section?)

Thanks everyone!

 

[Jeep Man]

Re: 25" Shaft Motor mounting w/ Jack Plate

Frankly, I wouldn't worry about a jack plate. Generally, a 20" motor is mounted at it's lowest or 1 hole from the lowest. In your case, if you mount it at it's highest position you'll be within a couple of inches of the same. A couple of inches too low on a pontoon won't make a noticeable difference. In fact, it could help a bit with occasional ventilation on sharp turns.

 

[Rancherlee]

Re: 25" Shaft Motor mounting w/ Jack Plate

I'd be more conserned about the ability of the current transom handling the weight of that 150hp Honda. It unlikely a 93' 24 foot 2 tube is built to handle a 150hp 4 stroke engine. I bent my 75hp rated transom on my 88' model due to my 70hp being over 100# heavier that the 70hp engine of years past.

 

[-dirt-]

Re: 25" Shaft Motor mounting w/ Jack Plate

Jeep Man - I already purchased the jack plate, and I like the adjust-ability of the jack plate. It should also be helpful on my center toon when I add it.

Rancherlee - My toon is manufacturer rated for a 115. I imagine they under-rate these to some extent. Regardless, I am adding some add'l support from the motor pod to the floor structure to support the extra weight. The motor pod is all-aluminum (bent 1/4" plate), with the transom being boxed 1/4" tube. Looks like my engine is ~100 lbs more than a Mercury 2-stroke 115. I agree this is not ideal, but it will have to make do until I get the center toon installed.

So does anyone see a problem with mounting the motor on the lowest setting on the jack plate?

Thank you guys!

 

[Rancherlee]

Re: 25" Shaft Motor mounting w/ Jack Plate

I don't see any issues since you took care of beefing up for now, didn't want to see ya loose that nice Honda 150 in the drink. I'm sure that the "capacity police" might barg into this post but as long as your state law allows it and the insurance company don't care go for it. There is a Pontoon capacity worksheet online that helps you figure out your capacities after your 3rd tube is added.

 

[-dirt-]

Re: 25" Shaft Motor mounting w/ Jack Plate

I picked up two 1/8" wall 2" square tubes in 8' lengths today. Going to add these add these as full-width trusses/floor joists in the stern for the motor pod to bolt to. It currently has 2" c-channel 1/8" aluminum joists on 21" centers. Also adding some stringers off the rear portion of the pod.

Can someone speak to what kind of steering cable/system I should use? It currently has a rotary style behind the helm, but the cable/rod appears bent at the motor tube end. It is also fairly stiff.

Should I replace just the cable, or the whole thing? Please recommend a brand/type...

Thanks!