Mercriuser 4 cly question

[lsf627]

Sorry if this was addressed previously, but I have not seen this one in any search. I was given a 1992 Searay 180BR LTD with a 3.0LX, and the block was cracked. I searched for a while for another 3.0, but gave up, and swapped to a 2.5L, figuring 20HP wouldn't make that much difference. Well I was way off. The 2.5 will only rev to 3900 RPM, and boat maxes out at 28MPH on GPS. The 3.0 would max out at 4400 RPM, and did 42 MPH on GPS. Is there that much difference with the 20HP loss, or am I missing something. The 2.5L valve cover states maximum RPM to be 4200-4600RPM.

What I had to do to get the 2.5 in there:

Change flywheel to one off a 165 6 cly (bolt pattern mismatch from 1985 crank to 1992 crank)
Install 3.0 head
Install electronic ignition from 3.0

everything else on the boat is the same from when the boat ran with the cracked motor.

17P aluminum prop on drive (not in the best of shape)

Thanks for any input

Any info on swapping to 4.3 would be greatly appreciated as well. Have not figured out how to mount the front of the 4.3 in the boat.

Thanks again,

Lee

 

[Lyle29464]

Re: Mercriuser 4 cly question

If everything is working right it looks like you might need to borrow a 15 inch prop. If that does not move it into the correct range I would recheck everything. gas timming advance look at plugs etc.

 

[bigdan1]

Re: Mercriuser 4 cly question

did you check if both flywheels had no balance weights ?


the big diffenrence between those two engines , is the amount of torque they produce...HP aint everything , torque is what gets your boat to plane .

like previously mentionned , i would try a 15p or 17P because your rpm being too low definitely calls for lower pitch .....

as for 4.3L swap , being too new to boats, ill wait for others to post on this !

 

[lsf627]

Re: Mercriuser 4 cly question

Gonna try a 15p prop today, keep u posted

 

[Howard Sterndrive]

Re: Mercriuser 4 cly question

Any info on swapping to 4.3 would be greatly appreciated as well. Have not figured out how to mount the front of the 4.3 in the boat.

I just did a 3.0 to V6 in my 1992 Bayliner.
details and $ budgeting (I had a free V6 to start with) here:
http://www.baylinerownersclub.org/forum/showthread.php?t=50922

one funny thing you might notice is my shift linkage.... I sold my 3.0 sans valve cover because the cover is the 3.0's shift linkage system...so I cut the valve cover into a bracket on the bandsaw and mounted it on the bulkhead....