4 cyl I/O to a 6 cyl in a Holiday

[grzzzz]

Has anyone up-graded from a 4 Cyl 120 to a 6 Cyl 150 on a Starcraft Holiday? I looked and looked at it in the garage all winter and convinced myself the only thing different between the 2 was about 6". Now, 6" could be a BIG length difference in some matters but on an engine box??? Well, it bolted right in. It's in and I should be on lake trial this weekend.

I was going to try a different prop pitch this year. "Circles" said that was what I needed. But, I opened craigs list a few weeks ago and found a glass organ donor with a 6cyl. It fired up, had good compression so in it went.

So, if the boat doesn't sink and I don't rip off the transom, I have a complete 120 with less than 10 hours on it. Complete rebuild for sale!!


Grzzzz

 

[dozerII]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Boat looks real good grzzz, it will be interesting to see what the performance difference is between the two. Keep us posted.

 

[jasoutside]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Agreed ^^^^

 

[GA_Boater]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Did you change the outdrive? The ratios are different between a 4 and 6 cylinder. Or was that the reason for a prop change? Keep us posted on the test.

 

[boatnut74]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Did you change the outdrive? The ratios are different between a 4 and 6 cylinder. Or was that the reason for a prop change? Keep us posted on the test.

I think the ratios are both 1.98 for the inline motors, when they went to the v6 it changed to 1.84 but I could be wrong.

I'll be interested to see the speed numbers with that 6 cylinder. I don't think there is more than 80 pounds difference between the 2 motors. Shouldn't be able to tell any difference.

 

[matt167]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Going from a 120 to a 165 is basically adding 2 cylinders to the same engine. The 4cyl was based off the same platform as the 6cyl. Pretty sure they share the same bore and stroke too. Even if the gear ratios are different, it shouldn't matter too much.

 

[grzzzz]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Thanks for the votes of confidence. I think I have already compensated for the weight difference. I move the gas tank 3/4 in front of CG under deck and the dual battery system I put in is in the bow. Live well in front of CG too. The killer is the weight of the 4 cycle motors. That 9.9 rude weights almost 100lbs. I'm always having to move the fat ladies to the front! I have several spare out drives. From what I can tell there are 2 basic gear ratios with the ones I have found. That was what I was trying to compensate for with the prop change on the 4 cyl. I'm hoping this increase in torque ...it will be just right.

Keep you all posted.

Grzzzz

 

[bob johnson]

Re: 4 cyl I/O to a 6 cyl in a Holiday

is your 6 cylinder the 250 chevy motor? didn't it have 165 hp?.......or did they make another one in 150 hp??? I have also seen motors that were 160 hp..and I think they were straight 6's too........ I took my old 6 cylinder the junkyard today before work....got $75...bob

 

[barato2]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Bob-- i think they're both the same motor, just different ratings in different years, sort of like how the 4 cyl went from 120 to 140 to 170hp but is still the same basic motor (changes are due to carb, electronic ign, .5 liter of displacement, and finally port EFI). all are theChevy "stovebolt" six, and you're correct that the four was created (i thnk for the early 60s Chevy II) by lopping off 2 cylinders of the six.

 

[grzzzz]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Bob, I believe barato is correct. I say 150 because that is what is on the valve cover. I have been told there are different carb "set-ups" that may account for the HP variations. From what I can tell it came out of a 75?

Grzzzz

 

[greg crosby]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Very interested in your engine swap. I have the dreaded 3.7 470 in an Islander 221. Love the boat but thinking of future repower. The idea of a chevy six sounds like the way to go. Anyone tried this?

 

[heyyou325]

Re: 4 cyl I/O to a 6 cyl in a Holiday

A marina put an 8 cyl 350 in mine and took out the 160 hp 6 cyl when they put the jet in in the 70's. I can't tell you the differences as I didn't own it then, but it still floats, at least part of the time. And Grzzzz you can raise the hp by changing carbs. I took out a plugged quadrajet and put in a performance edlebrock and a couple mechanics told me I should gain between 20 and 30 hp. Time will tell, it's not quite hooked up yet, and fishing season starts today.

 

[wtbarrong]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Greg - I have a 22 Super Sport that had the 3.7 470 in it and replaced it with the straight six. I had to move the front mount a little forward because of the extra length of the straight six. Plus I had to go with a larger pitched prop because I kept the 3.7 out drive. Other than those couple things - perfect swap out.

 

[grzzzz]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Ok gentlemen..... If I knew, I would have never rebuilt the 4cyl. Took it out Sunday for the first time. I had 4 extra large fisher persons, liquid refreshments for all, anchors, enough tackle to open a bass pro-shop annex... a 95lbs kicker hanging off the back that the prop drags in the water and throws a 6' rooster tail and it few right to 31mph GPS!!!! I used the prop that came with the 6cyl. I think because the Holiday is MUCH lighter than the glasser it came out of, I can even get some more increasing the prop angle. I was so giddy I forgot to even check the RPMs Sunday. Do that this weekend.

Grzzzz

 

[ezmobee]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Bob-- i think they're both the same motor, just different ratings in different years, sort of like how the 4 cyl went from 120 to 140 to 170hp but is still the same basic motor

Not 170. The 170HP was the dreaded 3.7L motor. 140HP was the highest rating for the 3.0L motor.

 

[barato2]

Re: 4 cyl I/O to a 6 cyl in a Holiday

i was thinking of the 3.0, not the 3.7, but you're right on the hp. i just rechecked GM website and they still list 140hp, even with port EFI. not sure where i got the 170 figure, unbless i was looking at the 177 ft lb of torque number.

 

[Bwana Don]

Re: 4 cyl I/O to a 6 cyl in a Holiday

What size is this boat? 18 footer? How fast are we going to get out of this 45 mph? I'm dreaming of putting a 4.3 in my Offshore. This is very interesting to me. Remove the gear, fishing buds and kicker, then let her rip. Check the rpm's and let us know.

Good job.
don

 

[grzzzz]

Re: 4 cyl I/O to a 6 cyl in a Holiday

That's the plan this weekend. I am just still getting over the difference. Just going over everything in my head one more time to make sure i don't make any mistakes. If you don;t hear from me Monday, send out the CG!!

Yes, 18-18.5 model

Grzzzz

 

[Bwana Don]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Coolio dude, I need a video, after the bugs are worked out of course. You may have blazed a trail for me Grzzz. I've been wanting more horses and I've not even splashed yet. The 4.3 was always my motor of choice, but the I6 is torquey. I like torque more than ponies. I love what you've done.

Be safe and be fast!
Don


Anyone know the torque curve on the 165 mercruiser?

 

[wtbarrong]

Re: 4 cyl I/O to a 6 cyl in a Holiday

Here is a nice thread about the I6.

http://forums.iboats.com/mercruiser...cruiser-165-inline-6-torque-curve-455778.html

I have one in my boat and absolutely love it. Had it rebuilt last year and is a perfect match with my 22' Super Sport - even with a boat load of people in it!