New boat engine swap question 3.0

[nitrosteve]

I have a 1986 3.0 140 hp engine that runs great no issue at all. I just bought 1998 Monterey 180 with a 3.0 but it has water in the cylinders. I only gave 500.00 for this boat/trailer and I want to swap my other 3.0 into it since the floor and transom is shot in the 1986. My question is can this be a direct swap or are there things I need to be prepared to change out. Any advice would be appreciated. Cant believe the deal I just scored I will post up some pics as soon as I get them.

 

[Bondo]

Re: New boat engine swap question 3.0

Ayuh,... It should be Plug, 'n Play.....

 

[nitrosteve]

Re: New boat engine swap question 3.0

So basically strip the 98 motor down to long block, and then do the same to the 86 motor then reinstall all the items off the 98 onto the 86. What about the flywheel?

 

[Bondo]

Re: New boat engine swap question 3.0

What about the flywheel?

Ayuh,... They each need their own....
The 86 uses the flywheel mounted coupler,..?? Right,..??

 

[nitrosteve]

Re: New boat engine swap question 3.0

Yes flywheel mounted, but I think maybe the intake is different mine has large port heads I think the 98 has a different port design.

 

[elkhunter338]

Re: New boat engine swap question 3.0

What about just taking the engine/outdrive off and swapping the whole thing. That way you do not have to pull parts off the engine. I would say do what ever seems simplest.

 

[nitrosteve]

Re: New boat engine swap question 3.0

What about just taking the engine/outdrive off and swapping the whole thing. That way you do not have to pull parts off the engine. I would say do what ever seems simplest.

That's a possibility but I would prefer to have the newer alpha drive than the 86 assuming the newer one works.

 

[nitrosteve]

Re: New boat engine swap question 3.0

Well here is the new boat its a little dirty but what do you expect for $500.00

 

[bigdaddypt]

Re: New boat engine swap question 3.0

that looks really nice...i hope you get the engine swapped fast and can enjoy it!

 

[nitrosteve]

Re: New boat engine swap question 3.0

So can I just use my intake and riser and forget about the heads being different? Are the flywheels and coupler the same on both engines?


To give you some history on the current 98 engine ran well for about an hour the first time the previous owner had it out then started sucking water into the combustion chambers, they thought it was carb related and rebuilt. But obviously the problem was still there. My gut tells me it was the flapper stuck but I think the engine is to far gone to revive it. It has sat for 2 years just as they took it out the last time. Im sure it has a cracked block after sitting through 2 harsh winters without being winterized. Now you understand why i want to swap. Has anyone done this before my biggest question is the related to the intake and riser will they fit? And the flywheel/coupler will it fit? Please help.

 

[nitrosteve]

Re: New boat engine swap question 3.0

I guess the help well ran dry on this one. Looks like im on my own. Ill post up the results when its finished just in case someone else is interested in doing this.

 

[fishrdan]

Re: New boat engine swap question 3.0

I think you nailed several things to check, port configuration on manifolds, flywheel, coupler, also check the carb (Rochester or Mercarb) riser (straight or offset), flywheel cover.

As far as I know, in the GM 4 cylinder marine engine family (140HP/120HP/2.5L/3.0L) there were:
2 different flywheels
2 different couplers
2 different flywheel covers
3-4 different manifolds
3-4 different heads
2 different risers
2 different carbs
3 different ignition systems
1 piece or 2 piece real main seal?
...probably others....

Whether or not the 86 is the same as a 98, I don't know.

 

[nitrosteve]

Re: New boat engine swap question 3.0

So far Ive found this out.
1. The splines on the coupler are the same so the drive shaft should fit in to the 86 coupler. But it will have to be aligned with the new style alignment tool.

2. The intakes are different mine has a large port heads the 98 has the small port heads. So I will have to use the 86 intake and riser.

3. Still not 100% on the old riser fitment to the newer exhaust pipe.

3. Ignition is easily swappable and I will def be using the newer one.

I would like some opinions though the 98 outdrive was obviously in salt water but its a gen 2 the 86 is a gen 1 but only saw fresh water all its life what would you use the old or the new? Thanks.

 

[fishrdan]

Re: New boat engine swap question 3.0

- check the distance between the rear motor mount bolt holes to make sure they are the same.

- check the length of the drive shaft

You will need to make a decision on which drive and transom assy you are going to use as they are not compatible. An Alpha 1 drive will not fit an Alpha 1 Gen II bellhousing, and the same the other way around

 

[JaseBosto]

Re: New boat engine swap question 3.0

Hands down I would use the Alpha gen 2. The only way I would not use it, is if it were visibly in poor condition. I run my boat in salt water, but run fresh water through it after and have no issues.

 

[elkhunter338]

Re: New boat engine swap question 3.0

2. The intakes are different mine has a large port heads the 98 has the small port heads. So I will have to use the 86 intake and riser.

Not necessarily I put a intake and riser from a 1971 large port head on a 2007 brand new engine. I was told use a special gasket 27-53354, I did and I have 130hrs on mine with no issues. The gasket is kind of a metal composit. The local auto/diesel mech that was helping me said that type of gasket should be fine in that application.

 

[nitrosteve]

Re: New boat engine swap question 3.0

Got the old engine w drive and transom assemble out in 3 1/2 hours today. Seemed to go very smoothly. Good thing for merc manuals.

 

[nitrosteve]

Re: New boat engine swap question 3.0

Well the swap is complete. I kept the Gen 2 outdrive but had to replace the shift cable and bellow. The engines where identical with the exception of the coupler. The older engine coupler has no extension for oiling the splines in the drive shaft. There was even holes for the shifting mechanism to mount to in the older head. We had our first official outing yesterday and everything went very smoothly. This was after 3 prior lake trials tweaking stuff without the family on board. It blows everyone mind that I paid 500.00 for this boat. I will post up some pics with it all cleaned up and lake ready.