converting 1988 150 to a 175-carb question

[Captain Koz]

Hello,
took a evinrude 175 powerhead and put it on a 1988 150 body. I used everything off of the 150... carbs, electrical, etc. My question is can I use the "1 1/4" carbs off of the 150 and rejet them or does the 175 require the 1 3/8 carbs?

 

[emdsapmgr]

Re: converting 1988 150 to a 175-carb question

I am assuming that the 175 you have is a flatback (149 cubic inch) model since it bolted right in place. The 175/150 crossflow blocks are the same. You should have no problem running the 1 1/4" carbs if the heads are the same p/n. It will make the same 150 hp. The 175 heads could be different, causing higher compression. The 150 XP/GT and the early flatback 175's all came with the larger 1 5/16" carbs and some came with different heads. You may want to look around for a set of the 1 5/16", esp if your 175 has higher compression heads. These larger carbs work well on the flatbacks, provide an easy hp increase and were used up to the 200 hp of early years.

 

[Captain Koz]

Re: converting 1988 150 to a 175-carb question

thank you!

 

[Benny1963]

Re: converting 1988 150 to a 175-carb question

hey koz and ems , i did the same thing both 149 cid flatbacks
used all my 150 elecs and carbs ,ran great plugs look good with no jetting
be sure to get your carbs clean clean clean ,my motor runs and idles well.
have know rejetted used some boysen reeds ,it has givin me a crisp idle ,a little better transition off idle and maybe and rpm or two on top end .
by the way ensapmanger been looking thru your old post on scream and fly
may pm ya for info on the intake mod soforth

 

[Captain Koz]

Re: converting 1988 150 to a 175-carb question

im actually amazed it started... it was a flatback powerhead off of a 1977 175 which fit onto a 1988 150. I had to strip off the exhaust cover, intake manifold, 2 port covers (the 88 had mounts for the solinoid) and the regulator (the 77 had an external regulator). A few gaskets later the thing started right up... 11 years difference. However, I am interested/concerned about the 175 running right like a 175. Im looking at a pair of 1 3/8 carbs instead of the 1 1/4 that came with the 150. What sucks is that I am already into it for 2 sets of jets with a 3rd on order... 18 jets at $7 bucks a piece. My thoughts were to rejet the 1 1/4 as prescribed for the 175 as per shop.evinrude.com. Despite all, im going to go with the 1 3/8's because I want as much power as I can. Why have it and not utilize it? Hopefully I will bolt those carbs on and not have any issues. i will have it done by the weekend but I wont know until the spring how it runs in the water under load. I have to sell my 225 first to make room on the transom. (the 225 is wayyyy too heavy for the hull... 1978 Aquasport cc, 20')

 

[emdsapmgr]

Re: converting 1988 150 to a 175-carb question

The 1 3/8 carbs were standard on the big block crossflows (160 cubic inch.) These carbs were setup to flow more air and fuel. You will have to really work with jetting them to get them to work on a stock low port 149 cubic inch model. You may find that they are slower out of the hole than the 1 1/4" carbs but will run stronger at top end. I believe there was one year the 150 XP/GT models used these large carbs. I'd look at the jetting that they used that year and start from there. Your 175 had stock 456/457 heads. These are good heads, used on the 150 through 200 models. Should be around 108-110 lbs compression. Probably the only (still around) heads that are better are the small bore 235 heads-the 872 and 873. Used for maybe 3 years starting in 1978. They will get you another 8 lbs compression. While NLA, they are worth scrounging around for. I'd also add the NLA rubber intake stuffers from a 200/235 and consider a set of composite reeds. If you plan any of these further upgrades, I'd hold off on jetting decisions till you make all the changes, as each can change jetting requirements.

 

[Captain Koz]

Re: converting 1988 150 to a 175-carb question

Thank you everyone. I will let you know how I make out with the 1 3/8's on the 175 in about 2 weeks. Im not sure if im going to water test or just test tank. Although I want to sell my 225 right off the transom, i am impulsive and may just swap them out to see how the 175 runs in the water. I will keep you posted as things result.

 

[Captain Koz]

Re: converting 1988 150 to a 175-carb question

Call me the last to know.... but is it true that the only difference between the 1988 150 and the 175 are the carbs? Are they the same block, pistons, crank etc?

 

[emdsapmgr]

Re: converting 1988 150 to a 175-carb question

No. In 1988 the two engines are completely different. The 150 is a 149 cubic inch flatback, the 175 is a 160 cubic inch bubble back with big carbs. These engines are not interchangeable due to the different exhaust adapter in the midsection. This thread is about putting a 1977 175 on a 1988 150 midsection.

 

[Captain Koz]

Re: converting 1988 150 to a 175-carb question

Great success!!! Shes running! I bolted on 1 3/8 carbs that I just got and rebuilt and she started right up... smootheeee... nice. Today during the day I will test tank her and see what I think. Trouble is I wont be able to boat test until I sell my 225 and clear the transom. Ill let you know how shes running

 

[Captain Koz]

Re: converting 1988 150 to a 175-carb question

Test tanked her today. Great success. Runs awesome. Cant wait to put her in the water as soon as I clear my transom. So in summary, I took the powerhead from a 1977 flatback and used it to replace the powerhead on a 1988 150 flatback. I had to change 2 of the intake port covers due to the accessory mounts on them. The 77 didnt have an installed rectifier however had the same cutout on top of the motor for where the 88 rectifier went (basically its the identical crank case). I used 1 3/8 carbs which I got on EBAY. The 150 came with 1 1/4 carbs. the part number for the 1 3/8's end in HO, which im assuming is High Output... which im not sure if it will be an issue intil I run her in the water. I plan on running her in the water and even if all seems well I want to do consistent spark plug checks to see if shes running lean/rich/perfect.
Anyone have any opinion/experience/comments on what I may expect from the 1 3/8 HO's. Is it going to work out or am I looking at a possible rejet? Which motor came with the 1 3/8HO's?

 

[Mclintock]

Re: converting 1988 150 to a 175-carb question

Great success!!! Shes running! I bolted on 1 3/8 carbs that I just got and rebuilt and she started right up... smootheeee... nice. Today during the day I will test tank her and see what I think. Trouble is I wont be able to boat test until I sell my 225 and clear the transom. Ill let you know how shes running

Re: converting 1988 150 to a 175-carb question

No. In 1988 the two engines are completely different. The 150 is a 149 cubic inch flatback, the 175 is a 160 cubic inch bubble back with big carbs. These engines are not interchangeable due to the different exhaust adapter in the midsection. This thread is about putting a 1977 175 on a 1988 150 midsection.

 

[Mclintock]

View attachment 399439

So this is on my 1985 vro 150 has somebody swapped carbs with a 175hp carbs and could this be my hard start issue?