Spectrum 1990 tunnel hull.

[MoblMec]

Hi Guys
I am a new owner of an older 1990 Spectrum 24" pontoon boat. This pontoon is different from a round tube pontoon. It has a hull like a offshore catamaran or tunnel hull boat. It looks like a V hull boat that is split down the middle of the V and 4 feet added in between. I am a sucker for tunnel hulls so I bought this and am planning an overhaul . The boat has a wore out 90 hp force on it and does around 20 mph . I want to change to a Mercury Black Max 200 hp and am hoping to get 40 mph out of it. I do plan on beefing up the tansom and that does not look to be to big of a project. Then recover the seats and rewire for lights and other accessories. I am wondering if anyone has any experience with this type of pontoon ??? Here are some pics. Thanks for looking.

 

[jbcurt00]

What's the max hp rating on your Spectrum? Suspect it's sub 150, and probably 120hp max

 

[MoblMec]

Don't know can't find the specs. Wait I just did 90 hp.

 

[ahicks]

A worthy project from where I'm sitting! Should do a really nice job in a chop. Still, 200hp may be a bit of a stretch. Check out the waterline with that relatively light 2 stroke 90 on it. Thinking that hull is really going to squat/struggle with the weight of a 200 on it. Kinda like a pontoon boat would.

Alum. boats are nearly always a relatively easy rebuild project.

Just for reference, I have an alum. deck boat that's almost that big at 22', but it has a more of a conventional shallow V bottom. Boat is 98" at the gunwales. It has no trouble getting into the 35-38 mph range with a 90 hp Honda using a 17" 4 blade stainless prop.

Point being, if your target is 40mph, I don't think you need that much power, and looking at the waterline on your transom, engine weight is going to be critical.....

2 pictures are to illustrate waterline. This boat has a very shallow draft (will float on a wet rag).

P.S. Last thought, you may get that boat apart and find it full of water logged foam flotation. That would be a good news/bad news kind of thing. Bad news is getting all that out of it is going to be unpleasant. Good news is that water line is going to change, as well as the boat's speed with 500-1000lbs of water logged foam removed.... -Al

 

[SpectrumAllan]

I just picked up the same boat! Have you found or did it come with any documentation? Owners manual or so on. I'm looking for some more exact specifications then what's on Nada. The guy I bought it from said it was rated up to 115hp.

 

[MoblMec]

I just picked up the same boat! Have you found or did it come with any documentation? Owners manual or so on. I'm looking for some more exact specifications then what's on Nada. The guy I bought it from said it was rated up to 115hp.

No did not get any kind of info with it. Just the info you saw on NADA. If you are going over 100 hp I would recommend beefing the transom that's what I am doing. I know a guy that has a 225 etec on his and he beefed the transom.

 

[jbcurt00]

Over Rated capacity is unadvised.

'Beefed' up transom transfers load/additional load to other parts of the designed transom, knee bracing and splashwell system that were only designed to carry the rated load, not just the weight.

used no 2 boats are the same, even the exact same model/make/year

Just the act of overpowering is considered reckless operation in some states, mine does, regardless of how moderately or diligent you treat the throttle

would never give or take advice advocating overpowering regardless of whose buddy did it, or how they did it.

 

[ahicks]

No did not get any kind of info with it. Just the info you saw on NADA. If you are going over 100 hp I would recommend beefing the transom that's what I am doing. I know a guy that has a 225 etec on his and he beefed the transom.

I'm not quite as paranoid regarding big power, though I'd leave the decision in your lap regarding if you want to do it or not.

Knowing pontoons as well as I do though, I'd have to see a picture of a 225 hp anything on a boat like this to believe it....

 

[clattin]

You guys with those 90hp Force outboards, are the lower units still good? I need one for my 1990 90hp Force.

Thanks!
Chris

 

[MoblMec]

You guys with those 90hp Force outboards, are the lower units still good? I need one for my 1990 90hp Force.

Thanks!
Chris

Chris my lower unit is good but my power head is weak with only 90 psi per cylinder. But sense it had two very low compression cylinders and would not run at all when I got it I am kinda happy. I have an extra parts motor with a lower it is the one piece drive shaft and the motor I am running is a two piece. Do you know what you have. And where are you at ?

 

[clattin]

Chris my lower unit is good but my power head is weak with only 90 psi per cylinder. But sense it had two very low compression cylinders and would not run at all when I got it I am kinda happy. I have an extra parts motor with a lower it is the one piece drive shaft and the motor I am running is a two piece. Do you know what you have. And where are you at ?

Mine is a 2 piece drive shaft.

Does anyone know if a Fiorce "L-drive" lower unit will work for my 1990 90hp? My understanding is that the L-drive was from a Force I/O and they used the same lower unit for the I/O and outboards at that time.