Engine Transplant

[Themanofsteel]

I have a 1998 Bayliner Throphy 21’ w/120 HP Mercury Force. The engine went out on me.

I came into 150 Mercury Engine from a 19’ boat.

The engine is about 4” shorter than the one on my Trophy. Can it still work or is it too short?

 

[GA_Boater]

Too short as in from the bottom of the skeg and top of cowling or from the anti-ventilation plate to the upper inside of the swivel bracket?

 

[sly_karma]

Would suggest it will still be underpowered. The weight of a 21 ft WA hull like your Trophy will do much better with a 200.

 

[Themanofsteel]

GA_Boater I measured both engines from where the engine sits on the transom, down to the tip of the fin below the propeller. Mine is about 4” longer overall.

 

[Themanofsteel]

sly_karma The specs says maximum for this boat is a 175hp. Id like a 200hp. I got this 150hp at a real deal but I was looking for a stronger motor.

 

[GA_Boater]

Measure down to the A/V plate - The larger of the two horizontal plates. About 20" for a long shaft, about 25" for an extra long shaft. The distance from the A/V plate to the bottom of the skeg doesn't count.

 

[achris]

When the engine is install, the anti-cavitation plate should line up with the bottom of the boat....

 

[Themanofsteel]

sly_karma The specs says maximum for this boat is a 175hp. Id like a 200hp. I got this 150hp at a real deal but I was looking for a stronger motor.

 

[Themanofsteel]

GA_Boater my original engine is 25” & the 150hp is 20”. Obviously to short. Anything I can do?

 

[achris]

GA_Boater my original engine is 25” & the 150hp is 20”. Obviously to short. Anything I can do?

Depending on the age of the 150, extension kits were available. Got a serial number for the 150?

 

[sly_karma]

sly_karma The specs says maximum for this boat is a 175hp. Id like a 200hp. I got this 150hp at a real deal but I was looking for a stronger motor.

Hmm. The USCG formula for max power derived from LOA and beam essentially ends at 20 ft, hull manufacturers set their own limits above that. 175 hp seems more like the low end of the power range rather than the max. I just know most hulls in the 20-21 ft WA configuration are mounted with around 200 hp. Those boats are made for saltwater fishing so the hulls are heavily laid up, plus the topside works add weight, as does all the fishing extras like bait tanks, downriggers, cannon balls, extra battery, heavy duty anchor and so on.

Sounds like you have more issues with that 150 than possible underpowering for your hull though. given the hassles I'm having with my 150, perhaps you could send that unusable unit my way...

 

[Themanofsteel]

achris serial 6366905. sly_karma I may consider selling it if it’s too much of a hassle extending it.

 

[Themanofsteel]

If I put that 150hp on my boat, will it still work being a bit shorter?

 

[Scott Danforth]

If I put that 150hp on my boat, will it still work being a bit shorter?

to idle around....maybe

to actually use the boat - NO

 

[GA_Boater]

It isn't the lack of power that prevents the 150 from working well, it's the prop will be a minimum of 5" too high so the water needed for the prop to work correctly will be blocked by the hull.

It's surprising and well documented how much an inch makes in performance and 5 inches will leave you very disappointed. As the boat gets on plane and the stern raises, the prop will be sucking air, not water.

 

[Themanofsteel]

Got. Ok

 

[Themanofsteel]

Can anyone recommend a extension kit. Not sure what will work on this 1983 Mercury 150 HP. Serial 6366905

 

[achris]

Doesn't look like an extension kit was available for those engines.

Another option, not my preferred, would be to have the transom cut down.... Or, disassemble the gear housing, fit an x-long drive shaft and shift shaft, replace the drive shaft housing and fit a longer water tube.... Not sure which way I would go either.... (being me, probably build up the engine as an XL )

Chris.....

 

[jimmbo]

If it is an 83, it will be a prop rated 150, very close to the same engine the pre 83 175 was

There might be Something like a Bracket that would mount the engine further back but not higher, even and inch or two lower, that offset should allow an engine 5" too short to run in solid enough water

 

[Themanofsteel]

Does anyone know if this 150 engine is oil injected.