Low profile motor?

[Rranger]

I have a 1985 mercruiser 5.7L that I hooked up to a SEI outdrive. It sticks up above the old floor level and I had to build a 12 inch high doghouse around the top of the motor. Which i don't like and with a smaller back deck think its a tripping hazard. The 1976 Fiberform used to have a type R tranny and blown engine i removed when I fixed it up. My question is there different height engines from the center of the cam to the top of the engine? I see ads for "low profile" engines but not much info. Ultimately I'd like to get a lower height engine so I can eliminate the dog house. Anyone care to share some knowledge?

 

[Bt Doctur]

depends, what was in the boat previously http://www.boatfix.com/merc/Install/gas/86017211.pdf

 

[Bt Doctur]

everything is based on crankshaft centerline in relation to outdrive height plus you need a minimum of 13 inches from water line to riser

 

[Bt Doctur]

The MC1, R,MR, Alpha1 , Alpha1 GEN II all have the same height so changing a drive does nothing

 

[GA_Boater]

For reference - What motor was in the boat originally that allowed a flat deck?

 

[harleyman1975]

Perhaps it had a ford motor like a 302?

 

[Scott Danforth]

the ONLY low profile gas motor that mercruiser offered was the failed Vaser. it was a 1.6 liter economy car motor turned on its side

you can get a new one on ebay. keep in mind - they all failed, they were dropped by mercruiser 15 times faster than the 470 was dropped

http://www.ebay.com/itm/NEW-Mercrui...ury-Marine-Boat-Engine-WARRANTY-/172022032555

all other spark ignited motors, be it v6 or v8 or 4-banger have a similar height from center of crankshaft to top of cylinder heads. while exhaust and induction systems may vary a bit, they dont very enough for one to be considered low profile. some of the old Renault motors were a bit shorter, however not enough either.

there are some lower profile diesels in the under 100hp range.

the fiberform originally had a MR drive, however that would not have changed the crank centerline or the height of the motor.

 

[Rranger]

The motor that was in it was half missing and thrown away 5 years ago so I have no idea what was in it. Not even sure if it was the original engine. The present floor is the same height as before I rebuilt the back end so that?s not the issue.

 

[ziggy]

ya've heard from the pro's now.
i'll give my layman's ideas. ie. just another boater.....

I have a 1985 mercruiser 5.7L that I hooked up to a SEI outdrive. It sticks up above the old floor level and I had to build a 12 inch high doghouse around the top of the motor. Which i don't like and with a smaller back deck think its a tripping hazard.

sounds like the 5.7L may not have been what it had in it before. assumption being that ya had to build the 12'' high dog house to clear the engine that it didn't have before. ya don't say how big or long yer boat is. mines 19'. everything onboard is a tripping hazard when i'm out on the water. mines just a small boat. i just put up with that idea. also, my rear deck is at most 2'. i have a inline 6 mercruiser engine. the front motor mount sits on the sole of my boat. the same height deck that i walk on. my dog house is as high as my rear deck deck and as high as the engine is on it's ft. motor mount. similar to you, i have a raised portion of my dog house to compensate for the extra height of the carb w/flame arrester. this is not a tripping hazard for me as i don't walk on my dog house.

The 1976 Fiberform used to have a type R tranny and blown engine i removed when I fixed it up

i'll assume a mercruiser R sterndrive. as in mc-1 revised. and you removed the old reminants of the old engine (be it orginal or not). that didn't have to have the 12'' dog house to clear the engine. ya may not know what it was. but surly ya know if it was a 4,6 inline or v, or eight cyl. engine. figuring out what it had might lead us to figure what fits in that particular boat w/o having to extend the dog house.unless ya just wanna keep yer v8. no matter what it had before. in that case, perhaps your 12'' high dog house may be the only answer. have fun with it. make it ram air or air induction

Ultimately I'd like to get a lower height engine so I can eliminate the dog house.

i don't understand that statement. big boats hide the engine below deck. small speedboats like mine have a dog house. no where to hide the engine. if ya got a boat similar to mine. i can't imagine being able to eliminate the dog house.

lastly, perhaps some pics might be helpful. it'd be fun to see yer '76 fiberform. last fiberform i saw on my watering hole made my mouth water. it was a sweet original 19 or 20 ft cabin cruiser....

 

[Rranger]

No Title

Ziggy thank you for your reply. I found a pic of the wrecked motor that was attached to the old R transmission and outdrive before I removed it. I followed the old floor line when I built the new floor with to be exact a 6- 8"riser around the engine. So the engine I installed the 5.7 for some reason sits 6-8" higher than the one in the pic. You can see the old floor stringers in the pic they barely clear the exhaust manifolds.
Just seems strange my 5.7 sits higher.

 

[Bt Doctur]

The small block V8 family is all the same height to the heads. There will be some variation in relation to the intake manifold used.
the 2 barrel or the hi-rise 4 barrel but the basic motor height is the same

 

[thumpar]

The intake is about the only thing I can think of that would be offered as a low/high type. Everything else is about the same. I can only see the intake height changing the overall height by a couple inches, if that, unless it is some kind of high rise.